How the hell is Grooveshark still alive? Essentially it's a streaming frontend for illegaly uploaded music.
You could argue the same about Youtube, in some sense. They do pay royalties to some artists, and at least for a while a lot of upcoming artists were advertising their new albums there. I discovered a bunch of great groups through that. Unrelated with revenue, but I liked how some artists (Avicii comes to mind) ask you what do you think about X song when you play it in Grooveshark, that's some valuable direct feedbac…
Rdio has a better interface, Spotify better social/apps, Pandora better radio. Grooveshark will die because it's only option is to eventually go legal, and then it loses it's only advantage.