Those anonymous comments you've been posting online might not be as anonymous as you think.

Last week, a Sacramento judge opened a small window of opportunity for a plaintiff in a lawsuit to discover the identities of individuals who had posted derogatory comments about him on a Davis blog.

The case mirrors others across the nation as courts struggle to balance anonymous speech online with the interests of litigants seeking information.

Many Internet user agreements warn bloggers that they aren't guaranteed anonymity. And more and more, those who file lawsuits are using the legal system to unmask attackers.

Online anonymity is "a speed bump that's relatively easy to clear for people with legitimate causes of action," said Matt Zimmerman, an attorney with the Electronic Frontier Foundation.

The San Francisco group is a leading advocate for anonymous speech on the Internet and is currently defending bloggers in Chicago against a subpoena by developers over comments against a controversial project.

A recent high-profile case in New York also highlighted the issue. Rosemary Port is suing Google after it revealed her as the anonymous blogger behind "Skanks in NYC," a site attacking model Liskula Cohen. A judge ordered Google to disclose Port's identity.

In the Sacramento case, a former police officer with the University of California, Davis, filed a lawsuit against the UC regents in February, claiming discrimination and breach of a settlement agreement in a prior lawsuit.

David Greenwald, who operates a blog called The People's Vanguard of Davis, wrote about the legal dispute, and his readers weighed in with comments.

Some of those comments, posted anonymously and under a pseudonym, caught the attention of the former UC police officer, Calvin Chang, and his attorney, Anthony Luti.

They believed UC insiders had posted the comments and wanted to find out who they were. In July, Luti served a subpoena on Google, the Vanguard's former host, demanding names, e-mail addresses and log-in information.

Google informed Greenwald, and his lawyer, Donald Mooney, filed a motion to quash the subpoena. He argued the information was protected by the First Amendment.

In a tentative ruling issued Tuesday in Sacramento Superior Court, Judge Shelleyanne Chang (no relation to the plaintiff) ruled mainly in Greenwald's favor.

But the judge said the plaintiff could pay an independent third party to perform an Internet address trace to determine if those who posted comments were the people he thought they were. Only then could their information be revealed, she ruled.

"The court agrees that if the comments posted on the blog were authored by 'managing agents' of the university, they would constitute evidence relevant to the existing claims against the university, including breach of the settlement agreement," the judge wrote.

Luti did not return a phone call seeking comment. Mooney said he and his client were unlikely to challenge the judge's ruling, even though it was not entirely favorable.

"The lesson is there are no absolutes in life," he said.

That's pretty much the state of the law, too, said Zimmerman, of the Electronic Frontier Foundation.

In general, he said, courts have been protective of the right to anonymous speech. Political advocates have long used pen names or written anonymously, he said.

But there have always been exceptions to free-speech protections, and the area has grown more complex with the explosion of bloggers on the Internet.

Only a few high-level appellate courts have taken up the issue, he said, leaving rulings mostly in the hands of lower courts.

In California, a leading case was issued by a state appeals court in San Jose in early 2008. Called Krinsky v. Doe 6, it involved the head of a Florida company who sought the identities of people posting nasty remarks.

The court said the First Amendment generally protects anonymous speech, even though the Internet's informality leads many "to substitute gossip for accurate reporting" and engage in "harsh and unbridled invective."

But where plaintiffs can make a plausible case for defamation, the justices ruled, online anonymity may be breached. "When vigorous criticism descends into defamation," they wrote, "constitutional protection is no longer available."

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