Thank you Jim.  I will add this to the followong reasons I just learned a
few moments ago:

"Botched" Schema update
Accidental deletion of OU (or any other object)
Database corruption
System State
Accidentally deletion of a DNS zone
Some DC's are also File/Print servers, DHCP, etc.

Some of these scenarios would require an authoritative restore or a complete
rebuild of the Active Directory, as some changes are replicated immediately.


...and as you mentioned Jim, time to synch. verses restore.