Comment: Re:So... (Score 1) 441
If I buy a book, crack the DRM, and send it to you, no publisher is going to have any idea I did it, watermark or not.
If I'm even a moderately serious pirate, I'm not going to balk at buying (or acquiring) an extra copy to do a diff with.
The only situation this addresses is the casual user who breaks the DRM and then uploads his copy for widespread distribution. That scenario seems to be very rare. If it wasn't, there'd be lots of copies of everything already available anyway.