I have already heard of a few cases of 'average' users dropping file sharing programs, afraid of receiving a call from authorities, especially to those people living on university campuses, having a few receiving warning notices, etc.
We have reported how the RIAA has been increasing efforts to fight file sharing, CNet has a story on a supposed drop of P2P apps usage since the end of June:

Nielsen/Netratings, a company that monitors Web traffic and desktop application use, said that use of top file-trading applications such as Kazaa and Morpheus have fallen by about 15 percent since the end of June. On June 25, the Recording Industry Association of America announced it was planning to file what could be thousands of lawsuits against individuals who trade copyrighted music online.

If you are interested, latest versions of Kazaa Lite supposedly feature some RIAA scanning protection, may be worth a shot.