Just like in Diablo or any other MMO, such as WoW, they have a massive database of keys that were created for the product. When you send a key in with your results, and they can;t match up that key with any they've created, then you're out of luck :-P. So they only way to get through is to have a key that's in the database. However, if you find one, it's already being used lol.
I think FutureMark is a wonderful company and does a lot of great things. Plus, their benchmarking software is out of this world. I think they deserve your $19.95