Grooveshark is no stranger to lawsuits, but the company may be facing its biggest battle yet — Sony and Warner this week joined in a lawsuit with Universal Music that seems clearly aimed at wiping the music service off the map. Universal filed the original copyright infringement lawsuit in November, alleging that Grooveshark executives personally uploaded illegal songs to the site. With Sony and Warner backing the suit, it effectively pits the entire inudstry against Grooveshark.

Grooveshark's long-standing defense has been the DMCA, which puts the responsibility on copyright owners to ask for infringing content to be taken down — it's the same "we can't be held responsible for what our users upload" defense YouTube uses — but if Grooveshark executives were indeed doing the uploading they'll be in quite a bit of trouble. Grooveshark vehemently denies the accusation, but internal emails that were part of Universal's original filings seem to indict it even further.