For people that are still deciding whether to get an authenticator, I remember someone in my guild would get hack almost every month, I know most of people in the guild in real life, and they are all pretty good with computer. Now I think about it, I can't remember anyone I know without an authenticator that didn't got hack, almost all of them got one eventually.
Blizzard is pretty good at handling hacked account, for WOW they usually restore your account and items within 24 hours. But lately hacker got a lot smarter, if they hacked your account and it doesn't have an authenticator, they will add their authenticator to your account using the free andriod/iphone version. That way you cannot even recover or reset your password using your e-mail address, since it will force you to input a code from the authenticator.
Have fun sending all the stuffs to blizzard customer services just to prove that it is your account, and be ready to lock out of the game for a few days. One of my friend had to start a new account because he couldn't prove the account belong to him (he pay with timecard, cdkey/receipt is long gone, e-mail got hacked too since it used the same username/password as Bnet account.)
It is not worth it =/