Accept email as username
Just an idea, but I believe it's a good practice for websites.
Sometimes we have different usernames for different web services (for instance, a user can use jhon or jhondoe when jhon is already taken), so it's a good practice to accept email as the username. In this case, the user doesn't need always to remember which is his username for that service. It makes life easier =)
Actually, you can just do that. I assume you don't want to share your email address with everybody, so you will have to set a Screen Name in your profile.
It's even possible to change your username if you want to. :)