[sebbecai]

I'd say that the ability to play any song (with playlists) without needing to install anything (Spotify) or pay money (Rhapsody) is the reason.

[timjahn]

I agree with both you, and the poster above you.

But I still wonder, how is Grooveshark still online legally? They let people upload their music and other people listen to it. It's basically Napster in 2012.