I have an email through my service provider.
I also have an email through yahoo and another through hotmail.

Pretty much use the hotmail, when you need to enter an email address, but wouldn't want to actually enter your own.
Conversely, the one through my provider is used by friends/family, to contact me.

I get 10 email addresses through the provider.
So just created 5 new ones, which are now the B.Net user names for my accounts.
These emails have never sent anything, any have only received the Blizzard B.Net confirmation email.

I won't use them to send anything.
Or as a username/email anywhere on the web.

It's not perfect, but guessing a username and a password combination, is a bit hard.
Already knowing the username, allows for brute force password attempts.
I suppose a keylogger could learn either, but that's what the authenticator is for.