(excerpt): Spam fighters say they need a good, strong federal law, like the Telephone Consumer Protection Act of 1991, which cracked down on junk faxes. Opponents of tight legislation, like the American Civil Liberties Union and the Direct Marketing Association, worry about free-speech restrictions. They also point out that an increasing amount of spam comes from overseas, which puts it beyond the reach of any American law.
One guy's anti-spam site: www.aboutspam.com