PlanetDungeonSiege has conducted an interview with Gas Powered Games' Kevin Lambert, in which the lead designer talks about a variety of Dungeon Siege II topics. Here's a snip about multiplayer cheating:
Q: A lot of players are asking about the problem of cheaters in multiplayer. Of course, short of a dedicated game server, we realize that GPG has very little control over the situation without resorting to hardcoding (which has adverse effects on modding capability). Can we assume that some of the more common hacks in Dungeon Siege have been patched in DS2 in an effort to improve the multiplayer scene?
A: We're definitely dedicated to providing a fun multiplayer experience for all DS2 players and will do everything we can to prevent hacking, cheating, griefing, or anything that would make playing online less enjoyable for players. One element that players will enjoy is that in addition to playing online, players will have the option to log onto their GameSpy account and store their multiplayer party data on GameSpy's secure servers.