It happens all the time and it sucks. I've been told that unless you have your name trademarked, there's nothing you can really do. This happens to all of the big and even small guys.
What you COULD do is run a WHOIS on the domain, contact the owner and try to work out some sort of deal with him. If I remember correctly, you don't have an affiliate program, but maybe you could offer something in return. Odds are he won't care and you'll just have to get over it.
A couple people pissed me off doing this. So guess what I'm doing? Taking the spots back.
