I developed a patch for the admin section that logs all changes made by the administrator. This is very helpful in tracking down configuration problems, especially in the environment with several independent admins. All entries are in the format "setting_name: 'old value' => 'new value'", and can be seen in log reports at /admin/report/log/index.php.
Patch is available at http://tracker.moodle.org/browse/MDL-11236, with hope that it will get merged into Moodle CVS.
If you ever wondered (like I did) who the &*^%@# changed the name format, enabled guest access or disabled a particular module without notice, this will save you from some frustration.
Jovca