One thing if people find out about this it should give people pause and pay more attention to their account security. Sounds like blizzard is tired of picking up the pieces for everyone elses mistakes.
After all how do they get the needed information to hack and steal accounts?
If I had to guess a lot of them at some point used services to buy stuff your not supposed to be buying and gave too much information or got infected with a keylogger when doing so.
Could have also fallen for a phishing scam and god knows how many other ways.
I know they do not just guess your information and get lucky