Could the president sue me if I posted a message critical of him?
No. With any free-speech issue pertaining to the Internet, established rules of First Amendment jurisprudence apply. If you were to post on a Web site a message criticizing a renowned scholar, a movie actor, or even the president, you could not be sued for libel unless “actual malice” was shown. See New York Times Co. v. Sullivan, 376 U.S. 254 (1964).
If criticism turns into threat, however, the situation changes. Threats are not protected speech.
Aren't ISPs required to conceal their clients' identities?
No. No law requires Internet Service Providers to protect users’ identities, or even to warn them if subpoenas have been issued seeking to reveal them. But some major ISPs and other online companies, such as Earthlink, America Online, Microsoft and Yahoo!, have made it standard practice to inform their subscribers of potential lawsuits against them.
Some states have laws against SLAPPs. Do they apply to online libel lawsuits?
At least in California, a court has determined that that state’s anti-SLAPP statute does apply to cyber-SLAPPs (Global Telemedia Int’l v. Doe in 2001). So far California is the only state where a court has ruled that way, but that does not mean other states do not apply their anti-SLAPP statutes to cyber-SLAPPs. (See SLAPP
topic in Petition.)