I've seen chip dumping in full effect. It has been devasting to see thousands of dollars gone wasted as two guys are obvoiusly dibbing in on the hands against their opponents.

I reported this certain occasion to pokerstars and they said that they had no proof of these 2 guys actually colluding because they did not have substational evidence. Pokerstars help service is great, but when it comes to colluding, they are less than great. I just think they don't want to lose players. It's a shame, really.