While I think that the music industry has bought it on themselves to an extent, with the costs of the music, I think that P2P programs should put some effort into stopping their illegal use. A lot of them quite openly advertise it as a source of 'free legal' music, games, movies and other programs. I guess they are worried, as there are not anywhere near as many legal uses of their software, as there is illegal.
Im no programmer, but wouldn't it be fairly easy to block out certain file types from the software?
On a slightly different note, shouldn't Kazaa be shut down for all the spyware, ad-aware and other junk in it?