I've personally bought more movies and music because I've downloaded songs or video from artists. Software is the same way with me. If there's a reasonable price tag on something I want, I'll usually download it and try it. If I like it or think it's worth the price, I'll buy it.
I don't think anyone could ever wipe out piracy. It's so easy nowaday's to transfer information, especially through the internet, that it would be impossible.
Think back to vhs and cassettes. If you wanted an album or movie you'd just put the tape in a 2 deck system and record it. The same thing is happening now, just more widespread. There's going to be people out there that make copying stuff their hobby, and most won't get caught. I understand why it's illegal and that production companies want to stop it, but I can almost guarantee it'll never happen.