It's up to the users to safeguard their account, not Blizzard. If you are hacked it is YOUR FAULT. I see a lot of ignorant posters here laying the blame (Wrongly) at Blizzards feet for instances where their character was hacked.
In 99% of situations yes, but for years Blizzard has failed to do anything about those hacking accounts from China who use proxys that can be filtered out of Blizzard did just a bit better with security.
I also remember when they added ads to their forums (forums btw only paying customers could post to so there was never any legitimate reason to put ads on it), the ad company they used actually put gold selling ads on the official Blizzard forums, and these pushed malware to the end user. Many people had their accounts broken into because of this, and all they did was go to the official blizzard forums. Took days for Blizzard to admit that it happened as well.