A suit brought by peer-to-peer specialist StreamCast Networks has Skype and KaZaA as defendants, among others.

The suit, filed in the U.S. District Court's Central District of California (Western Division - Los Angeles) alleges violations of the RICO Act, the Racketeer Influenced and Corrupt Organizations Act, brought about in the 1970s to combat the Mafia.
StreamCast Networks, maker of the Morpheus client, has named Skype, KaZaA, and the founders of both products, Niklas Zennström and Janus Friis, as defendants. Companies that helped develop the Morpheus software and the FastTrack peer-to-peer technology are also named. Currently, it’s unclear as to what allegations are being imposed against the defendants.