Blizzard has apparently struck the banhammer on “thousands” of Diablo III accounts as of this morning. In a post on the Diablo III forums, a GM wrote:
Also, just the other day Blizz updated the terms of service for using the Real-Money Auction House to include the requirement for a two-fold security system for your account if you wish to participate. You must have an authenticator tied to your otherwise simply password-protected account. You can use the free mobile authenticator app available for most smartphones or you can purchase a keychain-dongle for $6.50 from the battle.net store.
While some forum-goers have claimed their Diablo III accounts were hacked despite their using an authenticator, Blizz says it has yet to receive a confirmed report of a hacked account that had an authenticator attached to it… which was usually the same case for World of Warcraft accounts, after all fear mongering and rumors from people on the internet isn’t all that uncommon.