According to the New York Times, Harvard law professor Charles Nesson is challenging the music industry's filesharing witchhunt by attacking the basis for the lawsuits constitutionally.
From the site:
"Nesson argues that the Digital Theft Deterrence and Copyright Damages Improvement Act of 1999 is unconstitutional because it effectively lets a private group -- the Recording Industry Association of America, or RIAA -- carry out civil enforcement of a criminal law. He also says the music industry group abused the legal process by brandishing the prospects of lengthy and costly lawsuits in an effort to intimidate people into settling cases out of court."
