I've had experience with things like this before. I run a CD trading website and a few of our discs have wound up on eBay from time to time. Sometimes, it's questionable whether or not it's from us, but there was one occasion that gave the guy away. Myself and friends of mine sent him nasty emails and reported him to eBay multiple times in a few hours and he eventually just got annoyed and took them down. A similar strategy may work.