Can you send me a new password
Sent. You can recover the password for your account on the board using "Forgot password" link.
I was wondering if this method of recovering password can't be a problem for the big boards.
Well, he'll need to supply his e-mail with the request. This isn't very secure, too, and for large boards we would ask him to send us an e-mail from the address he's registered with.
And in any case before changing the password I store the old one (although I don't see it in plaint text but as an irreversible hash) so it can be put back if something goes wrong.