With the launch of Diablo III comes the inevitable spate of hacking concerns. Just today, I received an e-mail from Battle.net—a real one, that is—advising me to change my password as my someone other than me had apparently attempted to access it multiple times while I was logged into the game.
Though they failed at breaking into my account, numerous other users have reported that their accounts were hacked into—their passwords changed, and their inventory stolen.
The so-called "hacking" attempts are no doubt brute force attempts to break the passwords, or social engineering websites that trick users into giving up their username and password. Regardless of their methods, it's a good idea for players—especially those who value their inventory and progress in Diablo III—to pick up an authenticator from Blizzard or pick up the Battle.net Mobile Authenticator app for your phone.
You can grab either of them through the Battle.net account management page.
When you've got hundreds of hours worth of playtime on your account, it's better to be safe than sorry.