It will be quite valuable for users of services like Dropbox, Amazon Cloud Player, etc.
And sneakier still, a remote hosted bit torrent client that automates that process for you in a way that can provably show you never downloaded the copyrighted file, you just had a number on your drive, which if interpreted as a SHA256 hash key happened to identify a duplicate of the copyright file on Dropbox... (I'd be spectacularly impressed if someone managed to make _that_ trick fly on court in a precedent setting manner!)
I hope it doesn't happen, because that'd be a bit of a nightmare for Dropbox. They could blacklist known pirate rips of movies and the like, but what do you do when you receive a takedown notice for DRM-free content that some users are legitimately storing, but Dropbox is now (accidentally) illegally distributing? Could be the end of global de-duping.