EDIT: Is there a way to get rid of the "" account?
No. Generated coins need a place to go (they're credited to the "" account), and coins you send using sendtoaddress (where you don't specify an account) need to be debited from somewhere (they're debited from the "" account).
And it's theoretically possible somebody might could use one of your hidden "change" bitcoin addresses to send you coins; they'd be credited to the "" account, too.