Eric> NAT is what has prevented us from returning to the pre-1978 situation.
Keith> this is true only if you believe that [blah blah blah]
The situation today with NAT is that hosts in separate realms can only
communicate in 99% of the desired applications, though perhaps this falls to
80% if one stubbornly ignores the existence of tunneling and port
redirection.
Pre-1978, you were either directly attached to the Arpanet or you were
pretty much out of luck.
You have to be very much in the grip of a theory to regard these situations
as comparable.
Granted, it's easier to talk about the evils of NAT than to explain how
billions of new routable addresses are going to be added to the existing
routing system.