This enhancement has been requested through Moodle HQ.
User would like and enrolment plug-in that creates a group for each new user.
Administrator activates the new enrolment plugin at course settings.
New user finds a course that they want to enrol in. User creates user account. At that point the plugin automatically creates a group (groupname=username) and places that user into the group.
[the need for this functionality is so users can manually grade their own quizzes (and not see others)]