If Grooveshark did something like an artist revenue sharing program, I'd be more sympathetic to them. But they don't. I haven't seen Grooveshark really show interest in changing what is broken in the music industry. I see a company taking copyrighted work and throwing their ads next to them. Furthermore, taking customers' money to access special features related to the infringement.
Stolen cars can be bought for cheaper and with less paperwork. Ignoring laws does improve the Grooveshark experience. You say the laws need to be updated, but I honestly don't see what is wrong with a company holding rights to the music they produce. Grooveshark makes money off of copyright they don't own. Their own "Popular" featured section is chock full of infringement. They claim DMCA (a law I thought most techies liked), which is fine and well. Worked for YouTube. But they are going to have to defend that in court, and I have my suspicions that they might not be following the letter nor the spirit of DMCA.