Question: Which website contributes to the Slashdot effect and allows registered users to up or down vote submissions?

Context paragraphs:
Voat: Voat Inc is a news aggregator and social networking service where registered community members can submit content such as text posts and direct links.  Registered users can then vote for these submissions.  After accumulating 100 of these "upvotes" on original comments posted, users can begin voting against submissions and comments.  Voting is commonly called "voating" by users.  Content entries are organized by areas of interest called "subverses."

Smartfax: SmartFax Systems Incorporated is an internet fax provider that allows registered users to send and receive fax messages in digital format (. tiff, . pdf & . ps) via SmartFax's website or users' email addresses.  Established in 2004, SmartFax has been catering to small to medium-sized businesses within America and has been an alternative to traditional fax machines.

FFFFOUND!: FFFFOUND!  was a social bookmarking web site that allows registered users to share already existing images on the Internet and to receive personalized recommendations of other images.  Users not registered may view these posts and the corresponding recommendations; registration is strictly by invitation.  The site was established in 2007 by Yosuke Abe and Keita Kitamura of the Japanese company Tha, owned by Yugo Nakamura.

Slashdot: Slashdot (sometimes abbreviated as /.)  is a social news website that originally billed itself as "News for Nerds.  Stuff that Matters".  It features news stories on science and technology that are submitted and evaluated by site users.  Each story has a comments section attached to it where users can add online comments.  The website was founded in 1997 by Hope College students Rob Malda, also known as "CmdrTaco", and classmate Jeff Bates, also known as "Hemos".  In 2012, it was acquired by DHI Group, Inc. (i.e., Dice Holdings International, which created the Dice.com website for tech job seekers).  In January, 2016, BizX acquired Slashdot Media, including both slashdot.org and SourceForge.

Slashdot effect: The Slashdot effect, also known as slashdotting, occurs when a popular website links to a smaller website, causing a massive increase in traffic.  This overloads the smaller site, causing it to slow down or even temporarily become unavailable.  The name stems from the huge influx of web traffic which would result from the technology news site "Slashdot" linking to websites.  The name, however, is somewhat dated, as flash crowds from "Slashdot" were reported to be diminishing as of 2005 due to competition from similar sites.  The effect has been associated with other websites or metablogs such as Fark, Digg, "Drudge Report", Imgur, Reddit, and Twitter, leading to terms such as being "farked" or "drudged", being under the "Reddit effect"—or receiving a "hug of death" from the site in question.  Google Doodles, which link to search results on the doodle topic, also result in high increases of traffic from the search results page.  Typically, less robust sites are unable to cope with the huge increase in traffic and become unavailable – common causes are lack of sufficient data bandwidth, servers that fail to cope with the high number of requests, and traffic quotas. Sites that are maintained on shared hosting services often fail when confronted with the Slashdot effect.

Douban: Douban.com (), launched on March 6, 2005, is a Chinese social networking service website allowing registered users to record information and create content related to film, books, music, recent events and activities in Chinese cities.  It can be seen as one of the most influential web 2.0 websites in China.  Douban also owns an internet radio station, which ranks No.1 in iOS App Store in 2012.  Unlike Facebook and Renren, Douban is open to both registered and unregistered users.  For registered users, the site recommends potentially interesting books, movies, and music to them in addition to serving as a social network website and record keeper; for unregistered users, the site is a place to find ratings and reviews of said media.

Reddit: Reddit ( ) is an American social news aggregation, web content rating, and discussion website.  Reddit's registered community members can submit content such as text posts or direct links.  Registered users can then vote submissions up or down that determines their position on the page.  Submissions with the most up-votes appear on the front page or the top of a category.  Content entries are organized by areas of interest called "subreddits".  Subreddit topics include news, science, gaming, movies, music, books, fitness, food, image-sharing, and many others.  The site prohibits harassment, and moderation requires substantial resources.

Registered user: A registered user is a user of a website, program, or other system who has previously "registered."  Registered users normally provide some sort of credentials (such as a username or e-mail address, and a password) to the system in order to prove their identity: this is known as logging in.  Systems intended for use by the general public often allow any user to register simply by selecting a "register" or "sign up" function and providing these credentials for the first time.  Registered users may be granted privileges beyond those granted to unregistered users.

JamStudio.com: JamStudio ("JamStudio.com") is an Adobe Flash<nowiki>-based</nowiki> website that allows users to create music.  Formerly ChordStudio.com, the website quickly gained international popularity after its launch on June 1, 2007.  As of January 1, 2009, the site had 125,000 registered users in more than 160 countries.  JamStudio.com allows users to mix different instruments (guitars, drums, bass, etc.) with simple clicks to create music.  Created music tracks can be save as MP3s or saved online on the site.

Globule (CDN): Globule was an open-source collaborative content delivery network developed at the Vrije Universiteit in Amsterdam since 2006.  It is implemented as a third-party module for the Apache HTTP Server that allows any given server to replicate its documents to other Globule servers.  This can improve the site's performance, maintain the site available to its clients even if some servers are down, and to a certain extent help to resist to flash crowds and the Slashdot effect.  s of February 2011 the project is discontinued and is no longer maintained.

Supporting paragraphs: Slashdot effect Reddit
Answer: Reddit