Every client needs to have the information about what every other player is doing, to show that to the player, right? Thus, there is not necessarily any extra bandwidth requirement.
Servers can be authoritative about \"important\" stuff like rate of character level advancement, trade, etc. Also, a single attempt at cheating would probably just be logged as a statistic on the server when some number of cooperating machines agree. A pattern of detected cheats could lead to spurious devolvement of the character; there could also be public records of cheating statistics.
The game design could limit the rate of character advancement, accumulation of wealth, etc. It could be balanced such that even if you found a \"legal\" way to get lots of experience or lots of currency in a short period of time, the character server would limit the rate of gain.
Note that I\'m assuming someone with a little more authority stores the characters, to avoid local-side editing (a la phantasy star online), so I haven\'t yet figured out a good way of being TRULY peer-to-peer; only some ideas about how to greatly reduce the cost of running one of these games.
Too bad that Kiern left; he sounded so manly.