I am trying to figure out if Backups are single threaded.

Is there only one BackupSetWorkerThread, and only one account at a time is getting backed up, or are their multiple, and more than one account is being checked at a time.

Our auto-grouped (with zipped blobs) backups are taking more than 12 hours, yet we're not having our disk subsystem break a sweat. Seems we could shorten the window a bit if more than one accounts blobs were being retrieved at any one time.