I've just read this article which advocates using the sa account for ownership of sql server agent jobs.
He has a couple of caveats but doesn't provide much detail on these.
He does say the following:
...in situations where security is a concern, and where least privilege makes sense (such as with jobs other than backups, consistency checks, index defrags, etc.) then you'll want to look at AND take advantage of SQL Server proxies.
My question is - why does least privilege not make sense with backups, consistency checks, index defrags, etc? What is the rule of thumb for when least privilege can be ignored?