The music industry tells us that piracy is immoral because the artists that produce the music deserve the money from sales. But in most cases, it's the record companies and middle men that make most of the money, with the musicians getting the smaller share.
Musicians have other ways of making money, stuff like concerts and sponsors, and if people really like their music, then they'll feel obliged to pay for it anyway. Radiohead put their most recent album In Rainbows up on the internet with a 'pay what you like' system. It ended up earning more money than their previous album which was sold commercially, due in part, perhaps, to the absence of middle men.
I think that unless freedom of information on the internet is seriously restricted, there will be no way to stop piracy. Moral or not, it's the future.