I'm sorry, but I just don't get it. If the number isn't unique and can't be used and the network in question can NEVER attach to the Internet, why bother to get an officially assigned number at all?

That's easy. If you have users to use *assigned* addresses for isolated networks you can always catch a leak of the bogus routing information into the connected Internet. Try to do that with random adresses. The "isolated" networks very often have some physical connectivity to the Internet (backdoors, firewall machines etc) and the leaks aren't rare. --vadim