I got my acc banned 1 time, i suspect it had something to do with me using proxy to play Vindictus on US and then logged into wow without turning it off. (i know you can use programs to proxy only x application, but at the time didnt rly care about that). My acc got banned, i mailed blizzard with questions about how and why was it banned, within 24h of the mail the acc got unbanned and in game GM told me when i spoke to him, that it was mostly a measure from thier side to prevent any dmg to my account, because they go alerted of strange IP log in.
I didnt have auth at the time, have it now.
Also to add, i guess that if you have authenticator linked to your acc, things like strange ip login, shouldnt ring such a big alarm, since you acc is better protected and no matter the ip change, you still had to have auth to log in, while without auth it rly does look like someone is hacking your acc.