The logic here appears to be that since the employee is deemed to have paid the government on the day that an employee receives his or her paycheck, the employer is holding those funds in a trust for the government, to be remitted quarterly. The government appears to believe in Monteiro's strategy: "Fuck you, pay me." So you -- as an officer, an employee who pays bills, possibly a board member, or possibly other related parties -- can be personally liable if, for example, you used money from that presumptive trust to pay any other bill.

Although Internal Revenue Code Section 6672 includes officers, partners, and
employees, it does not exclude other individuals or firms that that can be
held liable. The IRS will first try to recover payment from the responsible
persons with the most liquid assets, but will also concurrently hold as many
people as possible liable, each with joint and several liability for this
100% penalty. There is no presumption of innocence in trust fund tax
situations. In Skouras v. United States, the court determined the assessment
on a responsible party is presumptively correct and issues relating to
willfulness could be resolved at the summary judgment level. The individual
has the burden of disproving by a preponderance of the evidence, the
existence of one or both of the elements that is willfulness or
responsibility. [1]

here [1] are some interesting horror stories:

Aside from the persons normally thought of as being responsible for these
taxes (CEO, CFO, President, Secretary, Treasurer, partner), the courts have
given fairly wide latitude as to which entities or individuals the IRS can
assign responsibility to. In 1987, the United States Supreme Court held that
the third party liability for trust fund taxes was affirmed against a lender
who paid employees’ wages with the knowledge the firm did not intend or
would not be able to make timely deposits of the trust fund taxes. In 1985
the courts found that a lawyer, who had power of attorney from the owner to
operate a car dealership, was found liable for the 100% penalty. In another
case the IRS determined that workers were incorrectly classified as
independent contractors and assessed the 100% penalty to the principals of
the firm. In a 1984 Revenue Ruling, the IRS stated that a volunteer member
of a board of trustees for a charitable organization can be held liable for
the 6672 penalty. In 1978 the United States Ninth Circuit Court of Appeals
determined that a general contractor was responsible for the trust fund
taxes not remitted by a subcontractor. An accounting firm was held liable as
a responsible party because it had failed to remit a client’s trust fund
taxes and paid creditors other than the Internal Revenue Service. The IRS
deemed the friend of a business owner responsible because he paid some
utility bills for the company, extended loans or pledged collateral on loans
to the company.

Imagine the shock when the IRS levied the Individual Retirement Account
(“IRA”) account of an officer of an S corporation and then included the
proceeds of the levied funds in the taxpayer’s Adjusted Gross Income for the
purpose of determining his earned income. The IRS used the constructive
receipt doctrine to conclude the amount levied from an IRA was a
disbursement – it had to be included as income. The taxpayer was further
refrained from deducting it as a pass through loss or a necessary business
expense. This is just a sampling of the many cases involving withholding tax
liability and the long arm reach of the IRS’ “responsible party” strategy. [1]

Like I said -- you can pretty fairly characterize this as, "Fuck you, pay me." Where I to own a business, I would strongly consider creating segregated accounts to hold the funds owed to the government. In fact, it would be nice if I could create a way to just pay the government every other week along with payroll so I would have no owed-to-the-government funds on hand to create temptation...

[1] http://papers.ssrn.com/sol3/Delivery.cfm/SSRN_ID2306636_code...