General developer forum

I'm developing a custom authentication plugin against a proprietary course registration system. While studying authenticate_user_login() in moodlelib.php, I noticed that it calls sync_roles() for each enabled auth plugin. The documentation comment for sync_roles() is not very helpful in explaining what its purpose is: "Sync roles for this user - usually creator". The function doesn't seem to be implemented by more than a few of the standard auth plugins either. Can anyone explain in more detail what the function is intended to achieve, or why I might or might not want to implement it?

Edit: This is Moodle 1.9.2.