Active Directory domain being shutdown-- Do I have to update my DBO accounts?
Yes, you need to change the databse owners to valid principals. There are several features that require the database owner principal to be valid, most notably the EXECUTE AS infrasturcture. You may be using these feature whithouth your knowledge, for example an application may be using SqlDependency which requires Service Broker which uses EXECUTE AS. Rather than face long nights of troubleshooting cryptic error messages, do yourself a favour and change all owners on all databases to sa:

alter authorization on database::&lt;dbname&gt; to [sa];


And no, I did not specify sa by mistake.