Yes. I'm registered with team advracer.net
The "prize" goes to the Wounded Warriors Foundation and isn't out of $$ range for most adventure racing type events, but the amount of time and work that goes into setting up an event like Tough Mudder far exceeds the average adventure race course setup. TM is fewer miles but more bang for your buck.
TM is good so is Spartan race, there are some other one time events too that aren't bad but far less epic. Check out http://www.pangeaadventureracing.com/
if you want in on more adventure racing events.
And, if you're pretty good at adventure racing team Earned Dirt partnered with ADVRacer.net is searching for a fourth. Strong navigation and trail running skills preferred. PM me if interested.