Have been a long-time lurker on these forums, registered just for this topic.
I was hacked a few months ago. Was taking a month or so break from playing, and my roommate told me my toon was online. I tried to log in, and they hadn't changed the password, only added an authenticator. I sent Blizz an email, and then called them. Got my pass changed, and set my battle.net to a new email.
Now, the best part is, this guy had put my account on a 1-month recurring subscription. Let's just say it still is. ;-) So yeah, I got hacked and now play WoW for free.
Also, only a couple items were missing, but I got them back.. none of the empty bag/bank horror stories you tend to hear.
if the hacker call his bank the bank will tell blizzard to pay the money back and blizzard will froze your account. So if your smart remove the credit card asap