Professional golfer Fuzzy Zoeller claimed that someone posted false statements about him on Wikipedia. Zoeller traced the IP address of the unknown author of the statements to a computer at Josef Silny & Associates, a Miami education consulting firm. Zoeller sued the firm for defamation, invasion of privacy, and intentional infliction of emotional distress. He filed the suit anonymously, but media outlets quickly discovered his identity. In the complaint, Zoeller alleged that the Wikipedia entry falsely stated that he had abused drugs and alcohol and mistreated his family.

According to USA Today, the paragraph in question was removed, but the information had been picked up by other websites. The lawsuit said it falsely alleged that Zoeller abused drugs, alcohol and his family.

Zoeller failed to trace the IP address to one specific person, and Josef Silny & Associates repeatedly denied that any of its employees had authored the statements. Several months after filing, Zoeller voluntarily withrew the lawsuit.

Zoeller did not pursue a claim against Wikipedia, and statements from his lawyer to the press indicate a belief that section 230 of the Communications Decency Act barred a lawsuit directly against the online encyclopedia.

Tennessee businessman Clark Jones sued WorldNetDaily.com, a socially conservative news and opinion website, and freelance reporters Charles C. Thompson II and Tony Hays for defamation in Tennessee state court, after WorldNetDaily.com published an article written by Thompson and Hays claiming that Jones had interfered with a criminal investigation, had been the subject of a law enforcement investigation into illegal drug trafficking, and was or had been involved in other criminal activities.  2d Am. Cmplt. ¶ 18.  Clark also sued the Center for Public Integrity, which had underwritten Thompson and Hays' reporting on the article and related investigative pieces, as well as other publications and broadcasters who repeated the claims made in the article.

During the course of the litigation, a Tennessee appeals court held that WorldNetDaily.com could not rely on statements of anonymous sources to make out its defense of truth without revealing the identity of those sources.  The Tennessee Supreme Court refused to hear the issue because WorldNetDaily.com did not take a proper appeal.

The parties settled out of court for an undisclosed sum in 2008.  As part of the settlement, the parties issued a joint statement, which said in relevant part:

Discovery has revealed to WorldNetDaily.com that no witness verifies the truth of what the witnesses are reported by authors to have stated. Additionally, no document has been discovered that provides any verification that the statements written were true.

Factual discovery in the litigation and response from Freedom of Information Act requests to law enforcement agencies confirm Clark Jones' assertion that his name has never been on law enforcement computers, that he has not been the subject of any criminal investigation nor has he interfered with any investigation as stated in the articles. Discovery has also revealed that the sources named in the publications have stated under oath that statements attributed to them in the articles were either not made by them, were misquoted by the authors, were misconstrued, or the statements were taken out of context.

WorldNetDaily.com and its editors never intended any harm to Clark Jones and regret whatever harm occurred. WorldNetDaily.com has no verified information by which to question Mr. Jones' honesty and integrity, and having met him, has no claim or reason to question his honesty and integrity. WorldNetDaily.com wishes him well. (source)

Brent Hanson, who operated a website focused on laser eye surgery called LasikFraud.com, posted allegedly defamatory material about Dr. Boothe, a refractive surgeon, essentially calling Dr. Boothe a quack and accusing him of botching surgeries. After Dr. Boothe sued Hanson, the parties settled the suit on January 31, 2005, with Hanson agreeing to a permanent injunction that required him to remove the offending allegations from his website and to delete all his digital content relating to Dr. Boothe, and restraining him from repeating the allegations elsewhere.

After the suit was over, Hanson apparently violated the injunction against him by posting more information about Dr. Boothe on different websites ("LasikQuack.com" and "LasikQuack.org"). Counsel for Boothe hired a computer forensics expert, who testified that Hanson controlled these websites, and attempted to conceal this fact by using eGold cards and offshore web hosting. The Texas court found that Hanson had breached the terms of the permanent injunction and was guilty of contempt. Hanson was fined $1,500 and sentenced to serve 540 days of jail time.

The jail term was suspended for 18 months on the condition that Hanson: comply with the permanent injunction; allow Boothe's representatives to enter his home and inspect his computers to check up on his compliance; refrain from erasing material from his computers (other than in the ordinary course of business); and withdraw any complaints against Boothe with government agencies (unless a court orders that he has a reasonable chance of success).

The court also ordered that all Internet service providers, domain name registrars,
web site administrations, search engines, UseNet Groups, computer message boards, webhosting companies, e-mail service providers, electronic currency companies, and other providers of electronic communications services or remote computing services and expressly including Google, Inc., DSLReports.com, BroadbandReports.com, and Yahoo!, and their respective corporate affiliates, to remove all links to LasikQuack.com, LasikQuack.net, and LasikQuack.org, as well as all text associated with those links, including any cached copies.

Lisa Krinsky, the former president, chief operating officer, and chairman of the board of SFBC International, Inc., a Florida company, sued ten anonymous defendants over comments about her posted to a Yahoo! message board. According to court papers, the anonymous forum posters made "scathing verbal attacks" against SFBC, Krinsky, and fellow corporate officers. (For juicy details, see Ars Technica's article on the case.)

Krinsky filed a lawsuit in Florida state court in January 2006 (the exact date is uncertain), alleging defamation and intentional interference with contractual relations. She served a subpoena on Yahoo! in California, seeking the identities of the anonymous forum posters. After Yahoo! notified the posters, one of them -- Doe 6 -- filed a motion to quash the subpoena in California state court. The court denied the motion to quash, noting (quite strangely) that Doe 6's conduct "appeared to be similar to federal cases involving "'pump and dump' stock manipulation efforts," although no claim to that effect was in Krinsky's complaint.

In February 2008, a California appellate court reversed the lower court's ruling. It held that Internet users have a First Amendment right to engage in anonymous speech, but this right must be balanced against a plaintiff's legitimate interest in pursuing a valid legal claim based on constitutionally unprotected speech, such as defamation. In striking this balance, the court rejected the "good faith" standard applied in In re Subpoena Duces Tecum to America Online, 2000 WL 1210372 (Vir. Cir. Ct. Jan. 31, 2000), indicating that this test "offers no practical, reliable way to determine the plaintiff's good faith and leaves the speaker with little protection." The court also declined to apply the test devised in Doe v. Cahill, 884 A.2d 451 (Del. 2005), arguing that the "summary judgment" terminology used in that case is "unnecessary and potentially confusing."

Instead, the court adopted a test that requires a plaintiff to make a "prima facie showing" that he or she has a valid legal claim against the anonymous speaker before allowing disclosure of the speaker's identity. The court made it clear that a prima facie showing required Krinsky to bring forward evidence (not just allegations) to support each element of her defamation and interference with contract claims, except for those elements that were beyond her control or dependent on the identity of the defendant.

Applying this standard, the court held that Krinsky had not made a prima facie showing on her defamation claim because the message board comments, viewed in context, constituted opinion protected by the First Amendment rather than statements of fact about Krinsky. The court further held that Krinsky could not make a prima facie showing on her interference with contract claim because this claim was based on the same constitutionally protected opinion.

Nam Tai Electronics, Inc., a Hong Kong-based electronics company, sued 51 "John Doe" defendants in California state court for libel, trade libel, and violations of California's unfair business practices statute.  The lawsuit revolved around negative comments about Nam Tai posted to a Yahoo! message board pertaining to Nam Tai. 

After filing the complaint, Nam Tai obtained a subpoena in California directing Yahoo! to disclose its subscriber data (IP address) for "scovey2," one of the anonymous forum posters.  Based on this information, Nam Tai determined that "scovey2" obtained his Internet access through AOL.   Nam Tai then obtained a "commission" for out-of-state discovery from the California court to depose AOL's custodian of records in Virginia, in order to seek identifying information for "scovey2."  Nam Tai asked a Virginia state trial court to issue a subpoena, and AOL moved to quash the subpoena. 

The trial court denied AOL's motion to quash, concluding that it would enforce the California "commission" and reasoning that First Amendment concerns implicated by the libel and trade libel claims were not implicated by the California unfair business practices claim.  The Supreme Court of Virginia affirmed, relying heavily on the principle of "comity" (that is, the respect states extend to the judgments of other states).  

The record is not clear regarding what happened in California court after the poster's identity was revealed.