I recently assisted a customer with missing OU's in Active Directory. We found that the OU's were not deleted (thanks to the AD Recycle Bin), but were actually moved to another OU instead. These occurrences can easily be prevented by using a feature that was introduced with Active Directory on Windows Server 2008. Now this is nothing new, but since we are still finding occurrences of this at our customers, I decided to publish this post as a reminder to review all OU's in your Active Directory forest, and ensure they are protected from accidental deletion.