Legal Question in Technology Law in California

I don't believe you're going to find a statute making it illegal, in the sense that you could be fined or jailed for doing it, or even be made to stop. We have a First Amendment right of free speech. However, there are practical limits to what you can say about John Doe in public, whether the forum is a soapbox in Times Square or a blog on the 'Net. Untrue and defamatory statements will get you a lawsuit for slander or libel. Even true statements can be actionable in a private lawsuit if they give unnecessary publicity to embarrassing facts (naming a rape victim, discussing someone's diseases, etc.). I would recommend against posting information about others on the Internet if it is objectionable (by them) and unnecessary, whether true or not.