SD no longer honouring backup-on-mounting-drive

[Manu Chao]

Even deleting all files with the word Superduper in their name (incl. the application) did not fix the problem (ok, I kept the files in /private/var/root and /private/var/log).

Deleting the two files:
~/Library/LaunchAgents/com.shirtpocket.backuponmount.plist and
~/Library/LaunchAgents/com.shirtpocket.backuponmount-login.plist

however, fixed it. Which is probably not completely surprising. And since the problem re-occurred within about three months (it re-occurred two months ago, I only now got around to fix it) maybe there is a pattern as to what triggers the failure.