And this is what i do NOT want, as people can forget their e-mail-adress!
And then what? Even when they enter their username, they still receive an email to actually confirm the password request. When they don't know which email address they used, they can't perform a password reset with their username, either. Unless they then go through all their email adresses and search for the mail. But then they could just as well try all their adresses in the form until one matches.