<PAGE>
 
                                                                    EXHIBIT 10.4

                         REGISTRATION RIGHTS AGREEMENT

     THIS REGISTRATION RIGHTS AGREEMENT (the "Agreement") is entered into as of
December 15, 1998, by and among Shopping.Com, a corporation duly incorporated
and existing under the laws of the State of California (the "Company") and the
subscriber as named on the signature page hereto (hereinafter referred to as
"Subscriber").

                                   RECITALS:

     WHEREAS, pursuant to the Company's offering ("Offering") of up to Sixty
Million Dollars ($60,000,000), excluding any funds paid upon exercise of the
Warrants, of Common Stock of the Company pursuant to that certain Regulation D
Common Stock Equity Line Subscription Agreement of even date herewith (the
"Subscription Agreement") between the Company and the Subscriber, the Company
has agreed to sell and the Subscriber has agreed to purchase, from time to time
as provided in the Subscription Agreement, shares of the Company's Common Stock
for a maximum aggregate offering amount of Sixty Million Dollars ($60,000,000);

     WHEREAS, pursuant to the terms of the Subscription Agreement, the Company
has agreed to issue to the Subscriber, from time to time, Commitment Warrants
and Purchase Warrants, each as defined in the Subscription Agreement, to
purchase a number of shares of Common Stock, exercisable for seven (7) years
from their respective dates of issuance (collectively, the "Subscriber Warrants"
or the "Warrants"); and

     WHEREAS, pursuant to the terms of the Subscription Agreement, the Company
has agreed to provide the Subscriber with certain registration rights with
respect to the Common Stock to be issued in the Offering and the Common Stock
issuable upon exercise of the Subscriber Warrants as set forth in this
Registration Rights Agreement;

                                    TERMS:

     NOW, THEREFORE, in consideration of the mutual promises, representations,
warranties, covenants and conditions set forth in Agreement and for other good
and valuable consideration, the receipt and sufficiency of which is hereby
acknowledged, the parties hereto agree as follows:

     1.  Certain Definitions.  As used in this Agreement (including the
Recitals above), the following terms shall have the following meanings (such
meanings to be equally applicable to both singular and plural forms of the terms
defined):

         "1934 Act" shall mean the Securities Exchange Act of 1934, as
amended, together with the rules and regulations promulgated thereunder.

         "Accrual Rate" shall mean X% per month, accruing daily from the date
that the applicable payment, as specified herein, begins to accrue, multiplied
by the applicable principal amount, where "X" equals one percent (1%) for the
first month following the date in question, and increases by an additional one
percent (1%) for each month that passes after the date in question, up to a
maximum of five percent (5%) per month; provided, however, that if the payments
resulting from such accrual are not paid to the Holder within five (5) business
days of the date they are required to be paid, "X" shall be deemed to have
equaled five percent (5%) from the beginning of such unpaid accrual until such
payments are made.

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         "Additional Registration Statement" shall have the meaning set forth in
Section 3(b).

         "Amended Registration Statement" shall have the meaning set forth in
Section 3(b).

         "Closing Bid Price" shall have the meaning set forth in the
Subscription Agreement.

         "Common Stock" shall mean the common stock, par value $0.01, of the
Company.

         "Due Date" shall man the date that is one hundred twenty (120) days
after the date of this Agreement.

         "Effective Date" shall have the meaning set forth in Section 2.4.

         "Filing Date" shall mean the date that is forty five (45) days after
the date of this Agreement.

         "Holder" shall mean Subscriber, and any other person or entity owning
or having the right to acquire Registrable Securities or any permitted assignee
thereof;

         "Piggyback Registration" and "Piggyback Registration Statement" shall
have the meaning set forth in Section 4.

         "Put" shall have the meaning as set forth in the Subscription
Agreement.

         "Register," "Registered," and "Registration" shall mean and refer to a
registration effected by preparing and filing a registration statement or
similar document in compliance with the Securities Act of 1933, as amended (the
"Act"), and pursuant to Rule 415 under the Act or any successor rule, and the
declaration or ordering of effectiveness of such registration statement or
document;

         "Registrable Securities" shall have the meaning set forth in Section
2.1.

         "Registration Statement" shall have the meaning set forth in Section
2.2.

         "Rule 144" shall mean Rule 144, as amended, promulgated under the Act.

         "Subscriber" shall have the meaning set forth in the preamble to this
Agreement.

         "Subscriber Warrants" shall have the meaning set forth in the above
Recitals.

         "Subscription Agreement" shall have the meaning set forth in the
Recitals hereto.

         "Supplemental Registration Statement" shall have the meaning set forth
in Section 3(b).

         "Trading Day" shall have the meaning set forth in the Subscription
Agreement.

         "Warrants" shall have the meaning set forth in the above Recitals.

         "Warrant Shares" shall mean shams of Common Stock issuable upon
exercise of any Warrant.

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<PAGE>
 
     2.  Required Registration.

         2.1  Registrable Securities. "Registrable Securities" shall mean those
              -----------------------
shares of the Common Stock of the Company together with any capital stock issued
in replacement of, in exchange for or otherwise in respect of such Common Stock,
that are: (i) issuable or issued to the Subscriber pursuant to the Subscription
Agreement or in this Agreement, and (ii) issuable or issued upon exercise of the
Subscriber Warrants; provided, however, that notwithstanding the above, the
following shall not be considered Registrable Securities:

              (a) any Common Stock which would otherwise be deemed to be
Registrable Securities, if and to the extent that those shares of Common Stock
may be resold in a public transaction without volume limitations or other
material restrictions without registration under the Act, including without
limitation, pursuant to Rule 144 under the Act; and

              (b) any shares of Common Stock which have been sold in a private
transaction in which the transferor's rights under this Agreement are not
assigned.

         2.2  Filing of Initial Registration Statement. The Company shall, by
              -----------------------------------------
the Filing Date, file a registration statement ("Registration Statement") on
Form S-1 (or other suitable form, at the Company's discretion, but subject to
the reasonable approval of Subscriber), covering the resale of a number of
shares of Common Stock as Registrable Securities equal to at least Eight Million
(8,000,000) shares of Common Stock and shall cover, to the extent allowed by
applicable law, such indeterminate number of additional shares of Common Stock
that may be issued or become issuable as Registrable Securities by the Company
pursuant to Rule 416 of the Act.

         2.3  [Intentionally Left Blank].
              ---------------------------

         2.4  Registration Effective Date. The Company shall use its best
              ----------------------------
efforts to have the Registration Statement declared effective by the SEC (the
date of such effectiveness is referred to herein as the "Effective Date") by the
Due Date.

         2.5  [Intentionally Left Blank].
              ---------------------------

         2.6  [Intentionally Left Blank].
              ---------------------------

         2.7  Shelf Registration. The Registration Statement shall be prepared
              -------------------                                            
as a "shelf" registration statement under Rule 415, and shall be maintained
effective until all Registrable Securities are resold pursuant to such
Registration Statement.

         2.8  Supplemental Registration Statement. Anytime the Registration
              ------------------------------------                        
Statement does not cover a sufficient number of shares of Common Stock to cover
all outstanding Registrable Securities, the Company shall promptly prepare and
file with the SEC such Supplemental Registration Statement and the prospectus
used in connection with such registration statement as may be necessary to
comply with the provisions of the Act with respect to the disposition of all
such Registrable Securities and shall use its best efforts to cause such
Supplemental Registration Statement to be declared effective as soon as
possible.

     3.  Obligations of the Company. Whenever required under this Agreement to
effect the registration of any Registrable Securities, the Company shall, as
expeditiously and reasonably possible:

         (a)  Prepare and file with the Securities and Exchange Commission
("SEC") a Registration Statement with respect to such Registrable Securities and
use its best efforts to cause 

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<PAGE>
 
such Registration Statement to become effective and to remain effective until
all Registrable Securities are resold pursuant to such Registration Statement.

         (b)  Prepare and file with the SEC such amendments and supplements to
such Registration Statement and the prospectus used in connection with such
Registration Statement ("Amended Registration Statement") or prepare and file
any additional registration statement ("Additional Registration Statement,"
together with the Amended Registration Statement, "Supplemental Registration
Statements") as may be necessary to comply with the provisions of the Act with
respect to the disposition of all securities covered by such Supplemental
Registration Statements or such prior registration statement and to cover the
resale of all Registrable Securities.

         (c)  Furnish to the Holders such numbers of copies of a prospectus,
including a preliminary prospectus, in conformity with the requirements of the
Securities Act, and such other documents as they may reasonably request in order
to facilitate the disposition of Registrable Securities owned by them.

         (d)  Use its best efforts to register and qualify the securities
covered by such Registration Statement under such other securities or Blue Sky
laws of the jurisdictions in which the Holders are located and of such other
jurisdictions as shall be reasonably requested by the Holders of the Registrable
Securities covered by such Registration Statement, provided that the Company
shall not be required in connection therewith or as a condition thereto to
qualify to do business or to file a general consent to service of process in any
such states jurisdictions.

         (e)  [Intentionally Omitted].

         (f)  As promptly as practicable aft becoming aware of such event,
notify each  Holder of Registrable Securities of the happening of any event of
which the Company has knowledge, as a result of which the prospectus included in
the Registration Statement, as then in effect, includes an untrue statement of a
material fact or omits to state a material fact required to be stated therein or
necessary to make the statements therein, in light of the circumstances under
which they were made, not misleading, use its best efforts promptly to prepare a
supplement or amendment to the Registration Statement to correct such untrue
statement or omission, and deliver a number of copies of such supplement or
amendment to each Holder as such Holder my reasonably request.

         (g)  Provide Holders with notice of the date that a Registration
Statement or any Supplemental Registration Statement registering the resale of
the Registrable Securities is declared effective by the SEC, and the date or
dates when the Registration Statement is no longer effective.

         (h)  Provide Holders and their representatives the opportunity and a
reasonable amount of time, based upon reasonable notice delivered by the
Company, to conduct a reasonable due diligence inquiry of Company's pertinent
financial and other records and make available its officers and directors for
questions regarding such information as it relates to information contained in
the Registration Statement.

         (i)  Provide Holders and their representatives the opportunity to
review the Registration Statement and all amendments or supplements thereto
prior to their filing with the SEC by giving the Holder at least ten (10)
business days advance written prior to such filing.

         (j)  Provide each Holder with prompt notice of the issuance by the SEC
or any state securities commission or agency of any stop order suspending the
effectiveness of the Registration Statement or the initiation of any proceeding
for such purpose. The Company shall use its best efforts to prevent the issuance
of any stop order and, if any is issued, to obtain the removal thereof 

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at the earliest possible date.

         (k)  Use its best efforts to fist the Registrable Securities covered by
the Registration Statement with all securities exchanges or markets on which the
Common Stock is then listed and prepare and file any required filing with the
American Stock Exchange, NASD and any other exchange or market on which the
Common Stock is listed.

     4.  Piggyback Registration.  If anytime prior to the date that the
Registration Statement is filed or during any Ineffective Period (as defined in
the Subscription Agreement)(but without any obligation to do so) the Company
proposes to register (including for this purpose a registration effected by the
Company for shareholders other than the Holders) any of its Common Stock under
the Act in connection with the public offering of such securities solely for
cash (other than a registration relating solely for the sale of securities to
participants in a Company stock plan or a registration on Form S-4 promulgated
under the Act or any successor or similar form registering stock issuable upon a
reclassification, upon a business combination involving an exchange of
securities or upon an exchange offer for securities of the issuer or another
entity), the Company shall, at such time, promptly give each Holder written
notice of such registration (a "Piggyback Registration Statement"). Upon the
written request of each Holder given by fax within ten (10) days after mailing
of such notice by the Company, the Company shall cause to be included in such
registration statement under the Act all of the Registrable Securities that each
such Holder has requested to be registered ("Piggyback Registration") to the
extent such inclusion does not violate the registration rights of any other
security holder of the company granted prior to the date hereof; provided,
however, that nothing herein shall prevent the Company from withdrawing or
abandoning such registration statement prior to its effectiveness.

     5.  Limitation on Obligations to Register under a Piggyback Registration.
In the case of a Piggyback Registration pursuant to an underwritten public
offering by the Company, if the managing underwriter determines and advises in
writing that the inclusion in the registration statement of all Registrable
Securities proposed to be included would interfere with the successful marketing
of the securities proposed to be registered by the Company, then the number of
such Registrable Securities to be included in the Piggyback Registration
Statement, to the extent such Registrable Securities may be included in such
Piggyback Registration Statement, shall be allocated among all Holders who had
requested Piggyback Registration pursuant to the terms hereof, in the proportion
that the number of Registrable Securities which each such Holder, including
Placement Agent, seeks to register bears to the total number of Registrable
Securities sought to be included by all Holders, including Placement Agent. If
required by the managing underwriter of such an underwritten public offering,
the Holders shall enter into a reasonable agreement limiting the number of
Registrable Securities to be included in such Piggyback Registration Statement
and the terms, if any, regarding the future sale of such Registrable Securities.

     6.  Dispute as to Registrable Securities, In the event the Company believes
that shares sought to be registered under Section 2 by Holders do not constitute
"Registrable Securities" by virtue of Section 2.1 of this Agreement, and the
status of those shares as Registrable Securities is disputed, the Company shall
provide, at its expense, an Opinion of Counsel, reasonably acceptable to the
Holder, of the Securities at issue (and satisfactory to the Company's transfer
agent to permit the sale and transfer), that those securities may be sold
immediately, without volume limitation or other material restrictions, without
registration under the Act, by virtue of Rule 144 or similar provisions.

     7.  Furnish Information. At the Company's request, each Holder shall
furnish to the Company such information regarding Holder, the Registrable
Securities held by it, and the intended method of disposition of such securities
to the extent required to effect the registration of 

                                       5
<PAGE>
 
its Registrable Securities or to determine that registration is not required
pursuant to Rule 144 or other applicable provision of the Act. The Company shall
include all information provided by such Holder pursuant hereto in the
Registration Statement, substantially in the form supplied, except to the extent
such information is not permitted by law.

     8.  Expenses. All expenses, other than commissions and fees and expenses of
counsel to the selling Holders, incurred in connection with registrations,
filings or qualifications pursuant hereto, including (without limitation) all
registration, filing and qualification fees, printers' and accounting fees, fees
and disbursements of counsel for the Company, shall be borne by the Company.

     9.  Indemnification. In the event any Registrable Securities art included
in a Registration Statement under this Agreement:

         (a) To the extent permitted by law, the Company will indemnify and hold
harmless each Holder, the officers, directors, partners, legal counsel, and
accountants of each Holder, any underwriter (as defined in the Act, or as deemed
by the Securities Exchange Commission, or as indicated in a registration
statement) for such Holder and each person, if any, who controls such Holder or
underwriter within the meaning of Section 15 of the Act or the Securities
Exchange Act of 1934, as amended (the "1934 Act"), against any losses, claims,
damages, or liabilities (joint or several) to which they may become subject
under the Act, the 1934 Act or other federal or state law, insofar as such
losses, claims, damages, or liabilities (or actions in respect thereof) arise
out of or are based upon any of the following statements or omissions: (i) any
untrue statement or alleged untrue statement of a material fact contained in
such registration statement, including any preliminary prospectus or final
prospectus contained therein or any amendments or supplements thereto, or (ii)
the omission or alleged omission to state therein a material fact required to be
stated therein, or necessary to make the statements therein not misleading, and
the Company will reimburse each such Holder, officer or director, underwriter or
controlling person for any legal or other expenses reasonably incurred by them
in connection with investigating or defending any such loss, claim, damage,
liability, or action; provided, however, that the indemnity agreement contained
in this subsection 9(a) shall not apply to amounts paid in settlement of any
such loss, claim, damage, liability, or action if such settlement is effected
without the consent of the Company (which consent shall not be unreasonably
withheld), nor shall the Company be liable in any such case for any such loss,
claim, damage, liability, or action to the extent that it arises out of or is
based upon a violation which occurs in reliance upon and in conformity with
written information furnished expressly for use in connection with such
registration by any such Holder, officer, director, underwriter or controlling
person; provided however, that the above shall not relieve the Company from any
other liabilities which it might otherwise have.

         (b) Promptly after receipt by an indemnified party under this Section 9
of notice of the commencement of any action (including any governmental action),
such indemnified party will, if a claim in respect thereof is to be made against
any indemnifying party under this Section 9, deliver to the indemnifying party a
written notice of the commencement thereof and the indemnifying party shall have
the right to participate in, and, to the extent the indemnifying party so
desires, jointly with any other indemnifying party similarly noticed, to assume,
the defense thereof with counsel mutually satisfactory to the parties; provided,
however, that an indemnified party shall have the right to retain its own
counsel, with the reasonably incurred fees and expenses of one such counsel to
be paid by the indemnifying party, if representation of such indemnified party
by the counsel retained by the indemnifying party would be inappropriate due to
actual or potential conflicting interests between such indemnified party and any
other party represented by such counsel in such proceeding. The failure to
deliver written notice to the indemnifying party within a reasonable time of the
commencement of any such action, if materially prejudicial to its 

                                       6
<PAGE>
 
ability to defend such action, shall relieve such indemnifying party of any
liability to the indemnified party under this Section 9, but the omission so to
deliver written notice to the indemnifying party will not relieve it of any
liability that it may have to any indemnified party otherwise than under this
Section 9.

         (c) In the event that the indemnity provided in paragraph (a) of this
Section 9 is unavailable to or insufficient to hold harmless an indemnified
party for any reason, the Company and each Holder agree to contribute to the
aggregate claims, losses, damages and liabilities (including legal or other
expenses reasonably incurred in connection with investigating or defending same)
(collectively "Losses") to which the Company and one or more of the Holders may
be subject in such proportion as is appropriate to reflect the relative fault of
the Company and the Holders in connection with the statements or omissions which
resulted in such Losses. Relative fault shall be determined by reference to
whether any alleged untrue statement or omission relates to information provided
by the Company or by the Holders. The Company and the Holders agree that it
would not be just and equitable if contribution were determined by pro rata
allocation or any other method of allocation that does not take account of the
equitable considerations referred to above. Notwithstanding the provisions of
this paragraph (d), no person guilty of fraudulent misrepresentation (within the
meaning of Section 10(f) of the Securities Act) shall be entitled to
contribution from any person who was not guilty of such fraudulent
misrepresentation. For purposes of this Section 9, each person who controls a
Holder of Registrable Securities within the meaning of either the Securities Act
or the Exchange Act and each director, officer, partner, employee and agent of a
Holder shall have the same rights to contribution as such holder, and each
person who controls the Company within the meaning of either the Act or the
Exchange Act and each director and officer of the Company shall have the same
rights to contribution as the Company, subject in each case to the applicable
terms and conditions of this paragraph (c).

         (d) The obligations of the Company and Holders under this Section 9
shall survive the resale, if any, of the Common Stock, the completion of any
offering of Registrable Securities in a Registration Statement under this
Agreement, and otherwise.

     10. Reports Under Securities Exchange Act of 1934. With a view to making
available to the Holders the benefits of Rule 144 promulgated under the Act and
any other rule or regulation of the SEC that may at any time permit a Holder to
sell securities of the Company to the public without registration, the Company
agrees to:

         (a) make and keep public information available, as those terms are
understood and defined in Rule 144; and

         (b) use its best efforts to file with the SEC in a timely manner all
reports other documents required of the Company under the Act and the 1934 Act.

     11. Amendment of Registration Rights. Any provision of this Agreement may
be amended and the observance thereof may be waived (either generally or in a
particular instance and either retroactively or prospectively), only with the
written consent of the Company and the written consent of each Holder affected
thereby. Any amendment or waiver effected in accordance with this paragraph
shall be binding upon each Holder, each future Holder, and the Company.

     12. Notices. All notices required or permitted under this Agreement shall
be made in writing signed by the party making the same, shall specify the
section under this Agreement pursuant to which it is given, and shall be
addressed if to (i) the Company at: Shopping.Com, 2 101 East Coast Highway,
Garden Level, Corona Del Mar, CA 92625, Telephone No. (949) 640-4349, Facsimile
No. (949) 640-4374 (or at such other location as directed by the Company in
writing) and (ii) the Holders at their respective last address as the party as
shown on the records of 

                                       7
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the Company. Any notice, except as otherwise provided in this Agreement, shall
be made by fax and shall be deemed given at the time of transmission of the fax.

     13. Termination. This Agreement shall terminate on the date all Registrable
Securities cease to exist (as that term is defined in Section 2.1 hereof); but
without prejudice to (i) the parties' rights and obligations arising from
breaches of this Agreement occurring prior to such termination (ii) other
indemnification obligations under this Agreement.

     14. Assignment. No assignment, transfer or delegation, whether by operation
of law or otherwise, of any rights or obligations under this Agreement by the
Company or any Holder, respectively, shall be made without the prior written
consent of the majority in interest of the Holders or the Company, respectively;
provided that the rights of a Holder may be transferred to a subsequent holder
of the Holder's Registrable Securities (provided such transferee shall provide
to the Company, together with or prior to such transferee's request to have such
Registrable Securities included in a Registration, a writing executed by such
transferee agreeing to be bound as a Holder by the terms of this Agreement), and
the Company hereby agrees to Me an amended registration statement including such
transferee or a selling security holder thereunder; and provided further that
the Company may transfer its rights and obligations under this Agreement to a
purchaser of all or a substantial portion of its business if the obligations of
the Company under this Agreement are assumed in connection with such transfer,
either by merger or other operation of law (which may include without limitation
a transaction whereby the Registrable Securities are converted into securities
of the successor in interest) or by specific assumption executed by the
transferee.

     15. Governing Law. This Agreement shall be governed by and construed in
accordance with the laws of the State of California applicable to agreements
made in and wholly to be performed in that jurisdiction, except for matters
arising under the Act or the Securities Exchange Act of 1934, which matters
shall be construed and interpreted in accordance with such laws.

     16. Execution in Counterparts Permitted. This Agreement may be executed in
any number of counterparts, each of which shall be enforceable against the
parties actually executing such counterparts, and all of which together shall
constitute one (1) instrument.

     17. Specific Performance. The Holder shall be entitled to the remedy of
specific performance in the event of the Company's breach of this Agreement, the
parties agreeing did a remedy at law would be inadequate.

     18. Indemnity. Each party shall indemnify each other party against any and
all claims, damages (including reasonable attorney's fees), and expenses arising
out of the first party's breach of any of the terms of this Agreement.

     19. Entire Agreement; Written Amendments Required. This Agreement,
including the Exhibit: attached hereto, the Subscription Agreement, the Common
Stock certificates, and the other documents delivered pursuant hereto constitute
the full and entire understanding and agreement between the parties with regard
to the subjects hereof and thereof, and no party shall be liable or bound to any
other party in any manner by any warranties, representations or covenants except
as specifically set forth herein or therein. Except as expressly provided
herein, neither this Agreement nor any term hereof may be amended, waived,
discharged or terminated other than by a written instrument signed by the party
against whom enforcement of any such amendment, waiver, discharge or termination
is sought.

                                       8
<PAGE>
 
     IN WITNESS WHEREOF, the undersigned have executed this Agreement as of this
14th day of December, 1998.

                                     SHOPPING.COM


                                     By: /s/ FRANK W. DENNY
                                        ------------------------------
                                         Frank W. Denny, Chairman

                   Address:          Shopping.Com
                                     2101 East Coast Highway, Garden Level
                                     Corona Del Mar, CA 92625

                                     Telephone No. (949) 640-4393
                                     Facsimile No. (949) 640-4374


                                     SUBSCRIBER:
                                     SWARTZ PRIVATE EQUITY, LLC.


                                     By: /s/ ERIC S. SWARTZ
                                        ------------------------------
                                         Eric S. Swartz, Manager

                   Address:          1080 Holocomb Bridge Road
                                     Bldg. 200 Suite 285
                                     Roswell, GA 30076
                                     Telephone: (770) 640-8130
                                     Facsimile: (770) 640-7150