I am guessing the face recognition from the android is likely to have first preference. The thumb and other recognition may get future preference. If the new account opening also goes through this method. In such case the spam and the usage of the gmail for spam would be surely reduced. I see many other such possibilities here. It's just that it is not yet there for us with current slow speed for the internet. Otherwise such recognition can be easily be done through servers for almost every type of authentication.