I am surprised at the number of people in my guild who say their account was hacked. I am also concerned that many of them seem like really poor thefts of people's accounts or gold. Every hack I have seen has been a "smash and grab" and never a real, professional style robbery. It makes me doubt that these people are really being "hacked". It seems more likely that they are getting gouged or ripped off by an ex-friend of some kind who knew their password. I tend to imagine that someone who got a key logger onto a system and got WoW information would take the hour or so to really clean you out. Your password would be changed, and once you reset it, you would log in and every character you had would be deleted. Clean sweep. Every item sold, every drop of gold mailed off to another account, and every single thing they can do to delay the inevitable report to Blizzard, done. I think a real hack is pretty rare. It's a lot of effort and work. And you would have to recoup every last bit of effort since you effectively violated federal computer intrusion laws to get someone's WoW account information. I suspect that the results of such a thing result in a complete and total milking of every virtual item found.
I think that account sharing, on the other hand, is not rare. I think a lot of people do it. And I also think a lot of people never change their password. Those are two very common things, in my opinion. Combined, an ex-friend, or someone you thought was a friend, is now enjoying your gold and hard work without leaving you totally crippled. It gets chalked up to evil hacking and Blizzard refunds the lost items. No harm, no foul, right?