People like it because it is LimeWire in a webapp.

Actually, scratch that -- they like it because it lets them listen to whatever the song they want to listen to, whereever they want to listen to it. As far as I know, nobody has that kind of selection anywhere else.

Youtube does, and is used as a main music player for a lot of people.

Yes, but youtube doesn't have an offline player feature and if it did, the videos would still be larger than Grooveshark audio.

But it is inconvinient for large playlists and is not, primerially designed for playing video.

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.

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.

There is a subset of music that is not available on the Spotify/Rdio net, for various reasons. If you don't have iTunes Match/Google Music/Amazon Cloud Player with this subset synced into, what do you do when you want to listen to a song now? You might find it on YouTube, or you might find it on Grooveshark.

I thought we got past regional bullcrap in 21st century as well. But as long as all other digital music stores and streaming services greet me with "Go away, you're not allowed to listen to us from your countrty" I'm happy to give Grooveshark money.