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

Stick to email addresses they are used everywhere, actually most of the major websites use them, they are unique so they save the user from struggling to find a name that's not used by others, also users won't forget their email addresses (in most cases at least :)), which is unlike usernames that they will keep on forgetting if they don't visit your site very often.

You shouldn't be worried about them being too long as all the major browsers (IE, FF .. etc) offer autocomplete to forms which is enabled by default, so you type the first letters in your email and you get a drop down list (ie. autocomplete list) where you just click to enter the whole email, personally I almost never type the email address in full, I always type the first letters then select the email from the autocomplete drop down list. Besides, if you allow users to be remembered (using a Remember Me checkbox and persistent cookies), it will be another reason to not worry about it.

I don't know about your app but usually users having multiple accounts is not desirable in most apps.