I agree, but what makes it hard shouldn't be having access to that number, it is verifying the number belongs to the person you are trying to impersonate. There is great need for an impersonal unique id for everyone - there are doesn't of people in the world who share the same name as me. It is possible that some of those people share the same birthday as me as well. For most purposes I want to go by my name, but when you need to be sure you need a unique ID.