I mix and add music tracks to many of my videos. I probably have spent a few thousand to own rights to use hundreds of tunes. Well worth the investment by not having to worry about getting my ass sued off.
It's pretty amazing how many sites out there rip-off all of their music.
Reality Kings was smacked with a major lawsuit for copyright infringement (which I believe they settled out of court), so I would say that anyone who rips music for their site, does so at their own peril.
ADG