Going after the BT sites is only a peice of the picture. Take a good look at the DMCA,
here's a link to an excellent analysis. In a nutshell, the big corporations want you to have no fair use rights. Look at your game collection, how many of us make a back-up copy just as soon as we buy a game? Well if your games were movie dvds or music cds and RIAA/MPAA had their way those back-ups would be illegal.