What are the pros and cons of using an email address as a user id?

Question

I\'m creating a web app that requires registration/authentication, and I\'m considering using an email address as the sole user id. Here are what I see as the pros and cons (upd

Answer 1

A good setup is to require username and email. Allowing the user to login with either email address or username is very user friendly. An added benefit is the user can change their email address. It would also allow multiple accounts for one email.