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

I think you missed a PRO:

Users are likely to remember their email address; and as email addresses are unique, they never have to worry about their preferred username being taken already.