Well, when I was younger, I was a fan of some obscure Japanese band whose music was simply not available in the US. I Limewire'd a few of their songs simply because there was no other way to listen to them, and I therefore felt I was in the right.
When I pirate video games, I usually stick to some guidelines. Either they're not all that great and sold poorly anyway (e.g. Saints Row 2) or they're rated M and I can't go to the store and buy 'em (I'm 16). I also never pirate indie games, since I figure they're hurt far more by piracy than Ubisoft or Activision or some such. And when I enjoy a pirated game, I try to go out and buy it when I have the money. If I had $50 lying around and wanted some new release, I'd go to the store and buy it. I never pirate if it is physically possible for me to get off my ass at that moment, go to a store, and come home with the game I want.
I'm really trying to lay off the piracy now, though. It's difficult, though, when you realize it's quite easy to spend $200 a month on new releases, older games I didn't get to, or expansions, DLC, etc. It sucks enjoying so many genres.