In November 2009, an Illinois Circuit Court judge ruled that Buffalo Grove Village Trustee Lisa Stone was entitled to pre-suit discovery of the identity of "Hipcheck16," an anonymous commenter who allegedly defamed her son in the comments section of a Daily Herald article.  The comments in question arose in the course of a heated political debate between Hipcheck16 and Ms. Stone's son:

The comments at the heart of the case came at the end of a series of posts between Hipcheck16 and Stone's son, who was concerned about online remarks the teen regarded as critical of his mother.

At one point, the teen asked to know the poster's identity and challenged him to debate the issues in person.

Declining an invitation to pay a visit, Hipcheck16 posted a response that said, according to court documents, "Seems like you're very willing to invite a man you only know from the Internet over to your house -- have you done it before, or do they usually invite you to their house?"

The post then continues with references to the boy's "mommy," saying that statements made by her son may cause her political problems after her election, according to court records. (Chicago Breaking News)

According to Chicago Breaking News, the newspaper turned over Hipcheck16's IP address, and Stone sought his identity from Comcast.  Although the record is not entirely clear, it looks like counsel for Hipcheck16 then intervened and sought a protective order, which the court denied in November 2009, though the court ruled that only Stone and a process server—should she file eventually file a lawsuit—could learn of Hipcheck16's identity.  

Later in November, the court granted a stay of the order for a month, to give Michael Furlong, Hipcheck16's lawyer, time to appeal.  Furlong told Chicago Breaking News that he intended to appeal.

Update:

03/15/2010 - EFF and The Media Freedom and Information Access Practicum filed an amicus curiae brief in support of Hipcheck16's appeal.

Elliott Madison (also spelled as Elliot Madison), along with Michael Wallschlaeger, was arrested by the Pennsylvania state police after using Twitter messages to relay information from police scanners and maps to protestors of the G-20 summit in Pittsburgh. They were charged with "hindering apprehension or prosecution, criminal use of a commnication facility, and possession of instruments of crime". According to Martin Stolar, Madison's attorney, the charge of hindering prosecution arose from the fact that Madison announced that the police had issued an order to disperse to the protestors.

A week after the G-20 summit arrest, Joint Terrorism Task Force agents searched Madison's New York home and seized his property, including his computers and the records he keeps for his occupation as a mental health facility counselor. Elena Madison, Jennifer Sobolewski, Michael Wallschlaeger, James Weiss, Irina Weiss, and Maik Hasenbank were also residents of this address at the time. The search warrant used in the search "asked for evidence that indicated...[potential] violations of federal rioting laws." If Madison is found guilty of violating the rioting law (18 U.S.C. §2101), he could face a penalty of up to five years in prison. Madison asked the court for a temporary order to prevent officials from examining the seized property until the court had the opportunity to examine the search warrant.  He also filed a motion to recover the seized property. Stolar argued that the search was unconstitutional and violated Madison's free speech rights. However, an Eastern District New York judge ruled that the government's search was not illegal and lifted the temporary stay, finding that the search warrant was "sufficiently particular and in compliance with the First Amendment".

The criminal charges in Allegheny County, Pennsylvania were dropped after the New York investigation commenced, as the law enforcement agencies felt that the G-20 activities "were not isolated incidents." Madison has not been charged in New York yet, and although he has attempted to appeal the court's order, officials are not prohibited from examining the property that they seized.

Dean Zuleger, the Village Administrator in Weston, Wisconsin, sent a letter to Paul Klocko, a local businessman, demanding that he cease making anonymous derogatory statements about him on the website for the Wausau Daily Herald.  Klocko had posted his comments on the Daily Herald's website after Zuleger was named Person of the Year by the paper.  According to the Associated Press:

Readers anonymously flooded the Wausau Daily Herald's Web site with comments bashing Zuleger's salary, his management style, his weight. One person suggested his third chin should have been nominated.

''I have just two words for Dean Zuleger, and they are ... A) anger management. B) salad bar. C) Rod Blagojevich. D) all of the above. The correct answer is D.,'' one posting read.

Zuleger asked the Daily Herald for the identity of the user behind the comments, and the newspaper complied with his request by releasing the e-mail address associated with Klocko's username.  Zuleger contacted the Daily Herald and demanded to know the identify of the commenter and the paper handed over one critic's e-mail address.

Zuleger then sent a letter on his official stationery, telling Klocko to stop the personal attacks and ''come out from behind the cloak'' and meet him.

The Daily Herald later apologized to Klocko for revealing his identity and the paper's corporate parent, Gannett Co., has clarified its policies on anonymous speech, stating that it will release information only if ordered by a court or if a comment contains a threat of imminent harm.

No lawsuit has been filed.

On July 4, 2009, an attorney for Alaska Governor Sarah Palin sent an open letter to Alaska blogger Shannyn Moore, the Huffington Post, MSNBC, the New York Times, The Washington Post, and other news organizations threatening to file defamation lawsuits if they claimed "as 'fact' that Governor Palin resigned because she is 'under federal investigation' for embezzlement or other criminal wrongdoing." 

Attorney Thomas Van Flein states in the letter:

To the extent several websites, most notably liberal Alaska blogger Shannyn Moore, are now claiming as "fact" that Governor Palin resigned because she is "under federal investigation" for embezzlement or other criminal wrongdoing, we will be exploring legal options this week to address such defamation. This is to provide notice to Ms. Moore, and those who re-publish the defamation, such as Huffington Post, MSNBC, the New York Times and The Washington Post, that the Palins will not allow them to propagate defamatory material without answering to this in a court of law. 

According to Politico, neither the New York Times nor The Washington Post "made any mention of the embezzlement rumors in their Saturday editions, but sources close to Palin consider the letter a warning shot to stay away from the topic."

Michael Patrick Leahy, author and founder of "Top Conservatives On Twitter," filed a lawsuit against blogger Stephanie Grasmick, Twitter user "Duke St. Journal," and 25 anonymous Twitter users for libel, false light invasion of privacy, intentional infliction of emotional distress, and tortious interference with contract.

Leahy, who appears to be handling the case himself, asserts that Grasmick posts on Twitter under the name StephanieInCA and is the operator of Teablogging, a site created "to chronicle the lead-up to the April 15 conservative hysteria Tax Day Tea Parties and to serve as a central repository for low-brow teabag-related sex jokes." His four-count complaint alleges, among other things, that Grasmick libeled him in a blog post on May 13, 2009, in which she falsely stated the he is:

• a "major tax fraud";
• a "delusional profiteering creep";
• an "insane clown"; and
• a "member of some alien race of Lizard People."

Compl. (First Cause of Action) ¶¶ 1-5.  Leahy also claims that Grasmick and Duke St. Journal repeated these false statements on Twitter.

Leahy also asserts a claim for false light invasion of privacy, although the conduct he complains about is more properly characterized as a claim for publication of private facts: the disclosure of his "residence in Williamson County, Tennessee."  Compl. (Second Cause of Action) ¶ 1. 

In addition to monetary damages, Leahy claims he is "entitled to see the complete records of all Facebook communications and telephonic commuications between Grasmick and her 283 Facebook friends, as well as public and private messages sent by Grasmick to those 469 persons she follows on Twitter, in order to determine the identity, if there is such, of any additional defendants who should be named in this complaint."  Compl. ¶ 18.

Update: 

May 22, 2009: Dispute resolved by mutual accord.  Leahy reported on his blog that "Grasmick has agreed to remove the false and misleading word from the headline of her May 13, 2009 blogpost which caused me to file a libel suit against her on May 18, 2009. I, in response, have withdrawn my complaint against her."  Grasmick confirmed the agreement and removed the word "fraud" from her previous blog post.