For those who care, a new case was just published by the California court of appeal holding that people who post in chat rooms or in forums have a First Amendment right to privacy.
Plaintiff, an officer in a corporation, served subpoenas on Yahoo trying to discover the identity of ten message board users she claimed had defamed her, and one of them ("Doe 6") objected and moved to quash the subpoena, saying he had a first amendment right to speak anonymously on the internet.
The court held that if there is actual, actionable defamation, it may be that production of the identity of the poster can be compelled. However, posting hyperbole and insults is protected speech, and the identity of the poster will not be compelled. The posts at issue were not factual; "[r]ather, they fall into the category of crude, satirical hyperbole which, while reflecting the immaturity of the speaker, constitute protected opinion under the First Amendment."
Case is Krinsky v. Doe 6, no cite yet.