I'm not sure I agree that insserv should completely abort when an unmet virtual dependency is unmet. There could be cases where one facility is missing, but its function is provided by another service.
I do agree though that insserv should not silently fail. With this in mind, I have patched insserv upstream to print a warning when a virtual facility is missing. This lets us know there is a potential problem without forcing a specific service to be installed for the initscript to work. The fix will be available in insserv-1.20.0. - Jesse
