Firstly, no one (not even the law) goes on Limewire, Kazaa, Morpheus, or etc and tracks down everyone's IP address. MILLIONS of people get mp3s of P2Ps, it's practically impossible to record EVERY one who uses P2P. And for the "people that download white noise", it's possible to listen before you get the file.
Secondly, yeah of course it's illegal as of July 2005. Personally, I do use Limewire, but just as a "try it" source, which is needed with groups like D4L flooding the charts. I wanna know what the album is like (good, bad) before I buy it, I'll just hint you here, it saved me $15 for not buying the Cassie album. Also, I sometimes get some current hit singles, for example, I'd get Me & U off LimeWire, I sure as hell don't want the whole album or want to pay $.99 for a 112-128 kb mp3 file. That's the other thing, the quality of most of the files are mostly bad, as you explain, a lot of "Temperature" files are probably corrupt just for people messing around on the program and trying to get ads out, and a lot of songs have skips and such, and 112-160 kbps files are...missing details and have pretty shotty bass.
Just to clear things up.