And as the cases move ahead, those accustomed to using the Web anonymously have a few things to think about, not all of them comforting, according to some First Amendment experts.
"These lawsuits are intended to intimidate people from speaking negatively about certain companies," said Barry Steinhardt, associate director of the American Civil Liberties Union.
Steinhardt said he believes this is true even in the most recent case, that of Seattle-based Wade Cook Financial Corp.
The company sued 10 "John Does" Monday for making allegedly defamatory comments about it on the Yahoo! board.
One contributor named in the suit, who went by the pseudonym "Delusional5," posted an erroneous allegation that the company's founder had been arrested for accepting kickbacks, according to the lawsuit.
"Delusional5" and the other defendants "used the anonymity of the Internet to damage the reputation and undermine the business of a legitimate company," Wade Cook attorney Paul Anderson told Reuters.
Falsely claiming in public that a CEO had been dragged off in handcuffs -- regardless of the forum -- would clearly be defamatory, the ACLU official and other observers said.
But they said they are disturbed by the possibility that a flood of litigation against people who participate in online discussion boards could stifle meaningful debate on the boards.
When rights collide
The tension lies between companies' legitimate need to protect themselves from disgruntled employees or ex-workers who make scurrilous postings in order to drive down stock prices, and the legitimate reasons for online anonymity, said David Sobel, general counsel at the Electronic Privacy Information Center.
"This is an assault on the concept of anonymity on the Internet," Sobel said of the Wade Cook suit and a similar suit filed last week against 21 "John Does" by Raytheon Corp.
In the Raytheon suit, the Lexington, Mass.-based company alleges the John Does are Raytheon employees who leaked proprietary technical and financial data on the boards.
While a worker's contract with his employer may bar him from discussing company secrets in public, the First Amendment may give him the right to do so, Sobel said.
Anonymous communiques protected
"The Supreme Court has said the First Amendment protects the right to communicate anonymously, so I do see a First Amendment problem with these cases," he said.
One problem is that under current law, there's no mechanism for notifying people who have made anonymous postings that a company is seeking their identity, Sobel said.
"A subpoena is required only when a government agency is seeking your identity," he said.
While Yahoo! officials said in both cases they would divulge the posters' names only if ordered to do so by the court, there's no law preventing them from doing so without a subpoena -- a potential violation of users' privacy rights, Sobel said.
Can't shout 'fire'
"There's no clear-cut procedure for how this would be resolved in court," he said. But the First Amendment, as the famous saying goes, doesn't allow Americans to shout "fire" in a crowded theater unless the theater really is on fire, another expert said. "Individuals have always had to take responsibility for what they say," said Liza Kessler, a staff attorney at the Center for Democracy and Technology.
Just because the statement is made on the Internet, that doesn't mean it's protected by the First Amendment if it is libelous, said Kessler.
"Presumably if you're just a crank and you're just posting lies about a company to get back at somebody, it eventually comes out," she said. "But people have to realize the Yahoo! financial boards are not the Wall Street Journal."