When I used to play Counter Strike (and more recently Halo), I would sometimes be the second-best player on my team - the best player being an order of magnitude better than me. In essence, I would get a low score until my team-mate left, due to him hogging all the kills.

As soon as that guy left, I would be able to play and would appear to get much better. This would lead to me being called a cheater, on the grounds of "you weren't that good just five minutes ago".