I don't understand how someone could sign up for a site with f.o.o@gmail.com in this example. That person would never receive email from the site (like a conf

I don't understand how someone could sign up for a site with f.o.o@gmail.com in this example. That person would never receive email from the site (like a confirmation), because the foo@gmail.com owner would receive the confirmation. Doesn't Facebook require confirmation before the account is created?