The anonymous user is a particular case which only serves the purpose of allowing one of the non-subscribed users to benefit from the courses publicly made available. The number of tracking opportunities is thus reduced. Note that if no course is made public, this user account is useless and could be disabled (although this feature is not officially supported).
Active/Inactive : the anonymous user can be enabled/disabled at wish
Courses list : the anonymous user cannot be subscribed to courses
Login as... disabled for the anonymous user
Statistics : the anonymous user doesn't show statistics
Edition : the anonymous user cannot be edited
Administration : the anonymous user can never be an administrator
Free/busy calendar : the anonymous user doesn't have a free/busy calendar
Removal : the anonymous user account cannot be removed (to avoid system incoherences)
Additionally to these management options, it is possible to remove all or part of the users by selecting the check-box on the left of the user and removing him below, as in the users management of a course for a teacher.