There is a (now widely know) which allows your Wizard to be 100% invincible on Diablo III. People been using it to show Inferno mode who is the boss.
I could not force myself to do it... beating Inferno with the bug is no different from beating Diablo on normal. You just waltz around, taking no damage.
I'm sure some people abused this bug before it was widespread, which makes the whole Auction House thing sounds kind hilarious. I can imagine a couple of guys profited madly with it.
The lesson *I* personally learned from it is to steer away from games which mix money and gaming. It's the difference between a casual card games with friends and poker for money.
Remember kids, the house always wins.