This is probably a extremely uncommon case, but:
What would happen if user A
registers an account in a website with an email that doesn't belong to him and uses it without confirming it (as many websites now allow you, at least in a limited way) and then some other person, user B
, tries to register an account with the same email which he actually owns?
Would a message "that email is already associated with an existing account" show, would it let both user A
and user B
access the site with the same email or what?