Quote Originally Posted by Zub View Post
meaning you would need 5 authenticators if you were to create 5 new bnet accounts today, if i understand correctly.
Correct.
Quote Originally Posted by Blizzard Authenticator FAQ
Can I apply my Battle.net Authenticator to more than one account?

Battle.net authenticators can now only be associated with one Battle.net account at a time. Please keep in mind that a single Authenticator will provide secure access to all of the World of Warcraft accounts associated with an individual Battle.net account.
So, technically, a single BNet would be the ideal route if you were going to use an authenticator (which is
obviously recommended).