In Moodle what controls the assignment of role to a new subscriber?

To clarify the question, what controls the assignment of role to a new subscriber (e.g. why are some people assigned the role of Teacher in some sites, and others the role of Course Creator in other sites)?

In Moodle 1.6 all users are considered guests who can self enroll into courses that are set to allow for course enrollment. There are some restrictions. A new subscriber can enroll in a course that is set to “course enrollable” and has an enrollment set only if they have the set enrollment key, which we utilize at the Grad School of Education. If no enrollment key is set than any subscriber can enroll in the course. A subscriber can only be a “Teacher” if they have been assigned the role of “Teacher” in a course.

In Moodle 1.7 you can set this explicitly. I don’t recall ever coming across an explicit setting for this in 1.6. In the Site Administration; Users > Permissions > User Policies. Here you set;

1. Role for Visitors
2. Default role for all users
3. Default role for users in a course
4. Auto-login guests
5. Hide user fields

This question came from Annelie Chapman, so let her know when you answer it.