One particular story clung. A player said that his "friend" got a chance to witness someone "win" $13k in one night cheating at online poker. I'm not too impressed with the usual tactics, run a background application to gather statistics on opponents or even the recent Absolute Poker cheating scandal. This one caught my attention because it was so simple, yet incomprehensible to catch. You could multiply the benefit with automation/a program, but that's not necessary.
The scam involved playing 5 of 6 simultanious accounts at an online poker table. It shouldn't take a superstar to see that you could easily squeeze out single unsuspecting victims. You could even use a program to obtain more accurate odds since you see 1/5 of the deck. Connection details seemed obvious. I would use proxy services to route via different cities around the world, consistent from each account. The crux of the scam lies in the fact that you can easily create throw away identities - violating the security pricipal of integrity, that you can verify that someone is who they claim. Online gaming sites do monitor IP addresses (defeated with proxies) and users who constantly collaborate. However, you'd be pretty hard to spot with a pool of accounts that get used for short time periods.
What about the penalty if you do get caught? I can't imagine playing multiple online poker accounts getting you in as much trouble as stealing...
The best protection brings inconvenience - closely couple user accounts with real people. That requires you to give up all the personnal info that you don't want to share: valid ID, bank accounts, SSNs, etc. As an online player I'd feel much more safe if the site required heavy verification. Then again, I only play online for "points".