Oh, piffle. NAT's don't "harm the Internet", any more than a host of other
things:
the fact that other things do harm doesn't mean that NATs don't also
do harm, or that the harm done by NAT is somehow lessened or excused.
and IMHO most of the other things you mentioned do less harm than NATs,
though I agree there are a lot of folks out there who are getting away
with screwing the net.
All of which leads me to a simple conclusion: one big reason that you and any
number of other people are upset about NAT's has nothing to do with their
technical shortcomings. Rather, what gets people so aggravated is that they
are killing off the "preferred" alternative.
The reason I'm upset about NATs is that they make it difficult to
build distributed and peer-to-peer apps, and they encourage a model
where the net is centrally controlled (not by a single center, but
by a relatively small number of providers who control the center).
I didn't get seriously interested in IPv6 until I realized that they
were the most likely viable solution to the NAT problem. In hindsight
I would have done IPv6 somewhat differently. But it's possible to start
IPv6, make applications work with it, and maybe fix a few things about
v6 along with way as people learn more about its shortcomings. NATs,
on the other hand, are completely intractable. e.g. even if you can
come up with a better solution to the firewall access problem (and
I think that's possible, though we're nowhere close to that now), as
long as you have NATs you're still stuck with the problems inherent
in a partitioned address space.
Keith