These days there seems to be a trend toward allowing forum users to log in with either their username or their email address, which I suppose users might consider convenient. But I rather like how MyBB does things: they allow the admin to specify one of three login methods:
- Users must enter their username and password
- Users must enter their mail address and password
- Users can enter either their username or mail address and password
I like this flexibility, mainly because I generally choose the second option. If you don't let users log in with their username, and users choose not to reveal their email addresses, their accounts will be somewhat more secure. (It's harder to brute-force your way past a password when you don't know the login ID either.)
Would it be possible to make the login method admin-configurable along these lines?