by Cyrak on Oct 08, 2010
Those of you who currently have more than one Battle.net account associated with a single authenticator will be able to maintain your existing setup without needing to do anything. This change will only affect new authenticator attachments. But, if at some point you decide to detach the authenticator from any of your Battle.net accounts for any reason, you won't be able to reattach it if it's already associated with another Battle.net account.
For more information on the Battle.net authenticator and mobile authenticator application (available for free with many mobile carriers), please visit http://us.blizzard.com/support/article/blizzardauth
If you're using a mobile authenticator or a normal Blizzard Authenticator for more than one account then you're going to have to go through some hassle or shell out cash for another one! This is probably going to cause more problems than it fixes, but I guess you can't be too careful (or can you?).