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

CON: Not everyone has an e-mail address. Consider if your database is ever accessed by an internal application. If you are running a store, people will call up and place an order by phone and refuse to provide an e-mail address. So while having an e-mail address as the default user ID is cool, be sure to allow alternates to get into the system. (Of course, this depends on the context.)

Learned this one the hard way.