IP: Confuses Me

I can't settle on an opinion about this. The more I read, the more I don't know what side my opinion falls on. I guess my opinion is: It always all depends. Do I think Napster was breaking the law? Yes, I certainly do. Do I think that Shepard Fairey's Hope poster was an infringement of intellectual property? No, actually, I don't. It seems to me that he took a photograph and turned it into a new, different, stylized and re-purposed piece of art. On the other hand, Napster's songs were the exact same ones I didn't want to pay for at the record store.

And this is where my opinion fails me. This is where law governing this kind of thing seems impossible.

The comparison of Napster's shared music to Fairey's stylized poster seems pretty cut and dry, but there is so much gray area in between. What about sampling someone else's music, in a new way, to create a new song? I understand the concept and reasoning behind protection, but I don't appreciate the way it seems to hinder creativity and prevent innovation.