When native FXA flag is turned on, we'll have to choose what email address to use for identity, either the "normal email" eg: amckay@mozilla.com or the firefox accounts email eg: ..093714548b9d@api.accounts.firefox.com For Bango, at least, any email we choose to be the identity is going to be the one credit cards get locked to. If we choose the former it means when users change their email, the credit card will be locked on the old account. If we choose the latter it means users can change their email, but all past credit card users are locked out.

we're going to use email instead of uid for now, to avoid breaking existing payments.