#Gmail allows users to insert dots anywhere in the username of their address, and still receive messages. A gmail username is tested for uniqueness with all dots removed. This is a nifty feature, which probably prevents some accidental mistakes leading to undelivered emails. On the other hand, it's often abused by spammers to get around unique email constraints in registration.
What do you think about preventing users from signing up with the same gmail account more than once? Heavy handed?
