Reading this will give you a good idea about whether or not you should be personally concerned about the actions and lawsuits of the mafRIAA or Media Defender.
A take-down program begins with the RIAA's list of about 700 current, popular titles of recordings owned by its member companies. The list is compiled - and continually updated - from Billboard and online music services' sales charts. The user-litigation program uses many more titles, but the RIAA won't disclose the number.
If you don't listen to the crap that the major record labels peddle then there is little to be worried about. Anyway other reports strongly suggest that they are just as likely to mistakenly target someone who has never even touched a computer. That is more of a concern.
Also note this article where the methods of the RIAA and Media Defender and their ilk are shown to be highly suspect and obviously ineffective:
Study Reveals Reckless Anti-Piracy Antics
...in May 2008, the team decided to repeat the tests, first to see if things had changed, and to discover if they could later implicate other IP’s, ’spoofing’ their presence. This time, there were almost 40% more DMCA notices, despite still not actually infringing copyright as claimed in the notices.