They're not even reasonable about uploading; I login to Grooveshark and go to "My Music" and click "Upload" and it asks me to upload my library, nowhere does it mention "oh btw if you don't own the rights don't do it", that's hidden on the terms of service page. The language used on the upload page is I'm sure well crafted so that they don't fall foul of the law but don't dissuade users from uploading: "...and only upload content that does not infringe upon the rights of others.". Why isn't that "Do not upload content that you are not licensed to distribute"?
I must be missing something.
Edit: to clarify for anyone that doesn't understand how Grooveshark works. They encourage users to upload their own music collection and do not at any point explain to the user that the music they're uploading is available to everyone or that what they're doing is illegal. Yes they're DMCA compliant but only at the very minimum required; if they wanted to be respectful towards labels/artists they could quite easily prevent people from uploading unlicensed material.