If you're one of the dozen or so who don't already have Jeff Jarvis' blog in a newsreader and check it daily, you should follow the link and read his rip on NJ state legislator Peter Biondi's really dumb bill that would outlaw anonymity in online conversation -- and make forum operators liable for any anonymous defamation.
In 1960, Justice Hugo Black gave us all a much-needed history lesson in Talley v. California:
"Anonymous pamphlets, leaflets, brochures and even books have played an important role in the progress of mankind. Persecuted groups and sects from time to time throughout history have been able to criticize oppressive practices and laws either anonymously or not at all. The obnoxious press licensing law of England, which was also enforced on the Colonies was due in part to the knowledge that exposure of the names of printers, writers and distributors would lessen the circulation of literature critical of the government. The old seditious libel cases in England show the lengths to which government had to go to find out who was responsible for books that were obnoxious to the rulers. John Lilburne was whipped, pilloried and fined for refusing to answer questions designed to get evidence to convict him or someone else for the secret distribution of booksin England. Two Puritan Ministers, John Penry and John Udal, were sentenced to death on charges that they were responsible for writing, printing or publishing books. Before the Revolutionary War colonial patriots frequently had to conceal their authorship or distribution of literature that easily could have brought down on them prosecutions by English-controlled courts. Along about that time the Letters of Junius were written and the identity of their author is unknown to this day. Even the Federalist Papers, written in favor of the adoption of our Constitution, were published under fictitious names. It is plain that anonymity has sometimes been assumed for the most constructive purposes."