It will just serve to make the p2p world devise ways to hide their actions from the plaintiffs (like peer blocking), or make them use the myriad alternatives that don't record ip addresses or removes the p2p aspect entirely (which is much lower "heat") such as youtube audio rippers, megaupload/rapidshare, usenet, or straight up http download services like beemp3.
If the mainstream "pirates" can't figure the above out (and, really if they can't, then how did they figure out bittorrent?), legit services like last.fm, pandora, spotify, or streaming stations from shoutcast and the like provide free music tailored to genres and user preferences.
Finally, perhaps people will just buy the damn things from itunes or amazon. I guess they'd "win" then.
