FUNDAMENTALS OF GAME DESIGN, SECOND EDITION
MODERATED CHAT SPACES
The most effective, but also the most expensive, way of keeping order in a chat space is to give one person authority to discipline the others at all times. Internet Relay Chat uses this method; the creator of a chat room exercises the authority to kick people out. If the enforcer also participates in the game, this method is subject to abuse. When people set up their own online matches among their friends, you can let them police themselves; but when they are paying someone to arrange the game for them (as in a match making service or persistent world), the moderator must be an impartial representative of the game's provider—a customer service agent, in effect, whether paid or unpaid.
Collusion is a form of cheating in which players who are supposed to be opponents work together in violation of the rules. The rules of Monopoly explicitly prohibit collusion. The fact that the players are all in the same room, and usually have social obligations to one another, tends to enforce that rule. Unfortunately, you can't count on those factors in an online game. Some players will join a game with a deliberate, even avowed, intent to cheat. Because they're playing with strangers, they have no social relationship at stake, and because they're physically miles apart, no one can see them do it.