Internet is build on dumb network, smart terminal. End-users are suppose to be able to put up their own services, not just running some apps. This has been the Internet principles and have serves us well so far.
(The telcos model, OTOH, is the inverse, assuming smart network and very very dumb terminal.)
-James Seng
What applications that people want to run--and the IT managers would want to enable--are actually inhibited by NAT? It seems to me that most of the applications inconvenienced by NAT are ones that IT managers would want to screen off anyway.