Diablo 3's real-money auction house is set to go live tomorrow, and when it does, it will require players use an authenticator for an "added layer of account protection," Battle.net's Meozeldian wrote. The authenticator, which comes in a physical version for $6.50 or as a free mobile app, will be required for anyone to add funds to a Battle.net balance.
Those who have already added funds to their Battle.net accounts will be able to use those without an authenticator, but from today on, all new additions will only work with an authenticator attachment.
Blizzard has previously suggested all players use an authenticator to prevent hacking, but this is the first feature for which it is a requirement. As this is to protect players' real money, it's difficult to find the rule egregious, especially as Blizzard generally handles thousands of hacks per day, and the mobile authenticator is entirely free.