Later on, I joined a different guild with different pranks -- most of them revolved around the fact that a good chunk of the guild was a bunch of guys that lived together or near each other. These guys all had each other's account information -- yes, it was a bad idea. No, you should never, ever share your account information with anyone; it's not only a security issue, it's against the ToS. However, there is also another reason you shouldn't share account information that was beautifully illustrated by the guild. See, we often grouped together to raid Zul'Gurub, AQ20 or AQ40 -- and if we were short a tank, one of the guys would log on his buddy the tank's account and tank the raid for us. That's pretty much why they were sharing accounts, so that we would have fill-in options if someone couldn't show for a raid.