Single or Multiple Battle.net accounts?

[Ualaa]

If you add an account to a battlenet email, you cannot transfer characters to or from the account for 30 days.
However, if both accounts are on the same battlenet email, this restriction is removed.

[ElectronDF]

I payed $0000 for adding an authenticator to an account. The mobile version is free and the physical version is $6 and no shipping. I use 1 autheticator number on 5 seperate BNet accounts and log in simultaneously. Until they change the mailing system, I don't have a reason to put them on one BNet. Again, pretty much no charge to use the authenticator, no matter how many accounts you have.