Think of it like any startup not checking if there are patents they infringe. If you think there's nothing wrong with the patent system, then you should be "pissed" about that too. But sane people tend to not be.
Does that mean this is legal? No, Universal and Pink Floyd (in addition to EMI) sued them and Grooveshark could not reach a deal with them. Apple even removed the iPhone app.
Nonetheless, Youtube started out the same way. I'm sure they will make more deals and become a legit company.
A while back they went legit and now have simulcasting deals with some of the anime distributors. You can get it the same day as Japan with your paid subscription, or get it for free the next week. At the same time, all of their old content was taken down.
I'm not saying I like this model, but it's been done before.