Steam

I'm not sure that would be the best solution. A cheater could still get caught cheating 6 times before requiring a repurchase, and it's still a pretty harsh penalty for someone who didn't cheat. You keep your game, but you can no longer share your library if your family situation changes.

'Sorry, son, you can't play my games on your computer because daddy made a bad decision when he was 21.'

The ultimate solution is probably an online identity when playing any game. Imagine if cheating got you banned from all online games for 5 years.