So, I have a few examples:
One of my friends won a game where he threw a fight. He went the economy/always host the games route and on the last turn, he invited himself to the games (unlike his usual MO of inviting the two strongest fighters to have one die). I send my guy, he sends his starter gimp. We all know he's going to lose, but only he and I know why: He has a reaction card that rewards a Dominus who lost a gladiator 1 influence (game over). Perfectly legit and I applaud him for the ingenuity.
In another game, one of my friends tried to throw a fight to cause a decapitation (he was really poor, placed 5 GP on it). The trick is, we all saw how we bet, so we all won. So, that doesn't work.
Throwing fights can happen (also in show and possibly IRHL) and is part of the intrigue. Really, any level of trickery/backstabbery is what makes the game so good. Now, if two people want to spin around the arena in a never-ending whirlpool, then, I'm not inviting them back to play this (or really, any other game) again. It's really that simple. We play to have fun, some also to win, but this type of action goes against both.
Edit: Slight show spoiler, but in the show, there is an instance where a gladiator wanted to make sure he died via beheading by telling the other gladiator while the fight is happening.