I have with a number of colleagues discussed the possibility to limit the access to creating new users to a selectable group just like the Helpdesk function and preserve the option of being able to access the form for non-authenticated people.
A lot of companies dislike the idea of self-registration, but would like to limit the creation of new users to a selectable group due to security reasons.
If the New User Form access is limited in the same way as the Helpdesk function with an option of being able to access the form for non-authenticated people, both self-registration and authenticated new user create would be possible.