In addition to thumbs up/down next to tracks, which has been requested already, add them to artists as well, but more importantly add them to the social sidebar to the right so users can directly give feedback to friends, and push select thumbs up/down to facebook.
You could also look into integrating a Like button for all artists to their Facebook page/fan page to connect their fans directly to them.
Then you could add a newsfeed with artist news pulled from fan page wall updates; this could be great because then you can track when your favorite artist is in town, and then you could add ticketmaster links and get a cut of tickets purchased!!
You're welcome! Now get to WORK!
I will take a free lifetime premium account as payment for my idea 😉