For years, the RIAA has claimed that having the IP address of a computer that has shared unauthorized files is the equivalent of having the evidence of who was actually sharing files. That, of course, is false. The IP address simply can help you know who paid for the internet access, but not who was using what computer on a network. In fact, this even had some people suggesting that, if you want to win a lawsuit from the RIAA, you're best off opening up your WiFi network to neighbors. It seems like this strategy might actually be working. Earlier this month the inability to prove who actually did the file sharing caused the RIAA to drop a case in Oklahoma and now it looks like the same defense has worked in a California case as well. In both cases, though, as soon as the RIAA realized the person was using this defense, they dropped the case, rather than lose it and set a precedent showing they really don't have the unequivocal evidence they claim they do.

I found this on Sam Smith's www.prorev.org