I did some game against a guy named "Garbonzo" once, where he made Antarctica a 50 bonus. The name of the game was copied from the auto-games.
I noticed in time and blocked him from taking Antarctica. The point is, if you notice, you can surprise the guy. But it isnt a game worthy remembering anyway. It got somewhat a taste. Though blacklisting bores me to death. I would play him again anyday.
Much more than these childish tries to rig the game, I dislike when your team member just bails out on you. That is really frustrating and then I really consider never playing with this guy again. Even if he is on the opponent team, there is no fun and I feel strongly urged to vote to end.