YOUR MOVE BLIZZ
They have already addressed this.
http://us.battle.net/d3/en/forum/topic/5149181449Battle.net®/Diablo III Security Concerns
Over the past couple of days, players have expressed concerns over the possibility of Battle.net® account compromises. First and foremost, we want to make it clear that the Battle.net and Diablo III servers have not been compromised. In addition, the number of Diablo III players who've contacted customer service to report a potential compromise of their personal account has been extremely small. In all of the individual Diablo III-related compromise cases we've investigated, none have occurred after a physical Battle.net Authenticator or Battle.net Mobile Authenticator app was attached to the player's account, and we have yet to find any situation where a Diablo III player's account was accessed outside of "traditional" compromise methods (i.e. someone logging using an account's login email and password).
To that end, we've also seen discussions regarding the possibility of account compromises occurring in ways that didn’t involve these "traditional" methods -- for example, by "session spoofing" a player’s identity after he or she joins a public game. Regarding this specific example, we've looked into the issue and found no evidence to indicate compromises are occurring in this fashion, and we've determined the methods being suggested to do so are technically impossible. However, you have our assurance that we’ll continue to investigate reports such as these and keep you informed of important updates.
The best defense against account theft still includes smart password management (e.g. using a unique password for every site/service and keeping your password to yourself) and scanning for malware and viruses regularly, as well as following additional preventative steps found here. In the end, while no security method is 100% foolproof, the physical Battle.net Authenticator and Battle.net Mobile Authenticator app are great ways to provide your account with an extra layer of protection.
We hope this update has addressed some of the concerns you've had. In the end, we simply want all of our players to be able to fully enjoy Diablo III, and we've been working around the clock to address issues as quickly and efficiently as possible. We appreciate your continued support and enthusiasm, and we hope you and your friends are having a blast slaying Sanctuary's demons.
What a surprise!! Blizzard denying that it's possible! What else would you expect them to do with literally BILLIONS of dollars at stake?