This is a bit old, but I just found out about it. Apparently, there's a one-man company that exists for the sole purpose of suing people who make use of his copywrited music through sampling. The company literally does nothing but acquire the rights to music...often in a shady fashion...in order to extort money from sampling artists.

http://www.slate.com/id/2153961/

"George Clinton is otherwise known as the King of Interplanetary Funk and, along with the late Rick James, the world's most famous funk musician. In the 1970s, Boladian and Bridgeport managed to seize most of the copyrights to Clinton's songs. How exactly they did so is highly disputed. However, in at least a few cases, Boladian assigned the copyrights to Bridgeport by writing a contract and then faking Clinton's signature (as described here). As Clinton put it in this interview, "he just stole 'em."

Bridgeport, if a thief, stole the winning ticket. The Clinton sounds it acquired went on to be among the most widely sampled in the rap music of the 1980s and 1990s. Sampling is as elemental to the genre as beats, beefs, or bragging, and Clinton's sonic creations were a major part of Public Enemy's debut, and were also used heavily by N.W.A., Dr. Dre, Biggie Smalls, and other rap pioneers. Often the sampling is virtually impossible to detect...in 2001, Bridgeport launched nearly 500 counts of copyright infringement against more than 800 artists and labels. The company, suing in Nashville, Tenn., located every sample of Clinton or other owned copyrights it could find."