I think google itself is a huge part of the problem. IMHO they simply try to take advantage of other peoples content. I was shocked last week to find so many "full movies" and "full albums" on youtube. And they do nothing against it.

The films shouldn't be there (apart from the ones you pay to watch), but the music (individual songs/albums) seem to be OK to upload by users who don't have the rights to do so, some labels seem to be OK with it, some aren't. It can act as advertising for the artists/labels and you get adverts on videos and some of that goes to labels/youtube/whoever.