There's a Street Fighter 4 machine near work. I went and played.
During one best of 5 contest, I won a match, then lost one, then won one, then lost one, then lost the tie breaker. On a hunch, I asked my challenger if he was letting me win. I was losing big, but also winning big, and something smelled fishy.
"Are you letting me win, or am I getting lucky?"
"Hm?"
"Are you letting me win, or am I getting lucky?"
"I-"
I realized he probably didn't speak English and dropped it.
The next match began and I think he understood what I was asking. He said, haltingly.
"I, uh, am letting, uh, you win, yes."
I knew it.