All the arguments for the legality of Grooveshark aside, it is ridiculously (read: Napster-like) easy to download high-quality MP3s from the service for free. Yes, there are rippers for Youtube and other services, but the quality of downloads is so spotty.
I watched a friend used GrooveShredder [1] the other day, which is a simple Firefox add-on. In 10 minutes, he had downloaded about 50 tracks. That alone made me realize that they were on their way out, so all the arguments for their legality are largely moot.
[1] https://addons.mozilla.org/en-US/firefox/addon/grooveshredde...