Seriously? Spotify and Grooveshark aren't even playing in the same league. Grooveshark's audio quality and music library are a wreck compared to Spotify's clean, consistent and reliable one. This is like people who decried the iPod and foresaw its doom because "Archos had the same thing available for 2 years." Not comparable.
I don't remember anyone calling it innovation. How about a nice feature addition to a service? After all, Spotify also has many other "innovations" Grooveshark doesn't: a clear legality, accurate track and artist catalogues, and paying all of their artists (even if it isn't much, it is certainly more than Grooveshark).