I was accompanying a friend of mine around a golf tournament years ago when he got a hole in one. The tournament prize was a brand new Mercedes. Unfortunately, my friend was the trainee golf pro at the club, and was playing as an employee of the club. This invalidated his win. He was actually pretty cool about this, but the tournament sponsors decided that they could then cancel that prize offering for any subsequent players. This was contentious amongst the other players, but no one else managed to get the hole in one, so no one had a valid reason to initiate an official protest. I still wonder about the technical validity of the sponsor's argument.