It's an interesting idea to thwart torrent piracy, it's got some holes as other people have mentioned. Not to mention some people who pirate a lot tend to get familiar with different pirate release groups and if a download isn't tagged with their favorite group's name then they'll probably steer clear or at least raise some eyebrows and ask questions before snatching it.
A more advanced method might be to have a server act as a seeder for an already released "real" version of the game and simply Seed corrupt data, if they give it some good bandwidth and make it look like they're seeding the whole thing I'm sure all the torrent clients would leach from it like moths to a flame but of course they would be just spinning their wheels because every packet would fail CRC and try again... it wouldn't stop it completely but it would probably slow down the process to a snails crawl. And unless you could determine who exactly was sending you the bung data it'd be hard to stop.
Then again that might only work on public trackers.