Among all adjectives to describe the security issues of NAT, "few" is not one of them. _Especially_ when you remember that many are under the false impression that they are "protected" by NAT.
don't get me wrong, i like a global address space as much as the next internet native, but it's not for everyone to pay the price for it and nat makes it easy to opt-out of a large portion of the problem space.
[1] my university used to give public-routed v4 to students connecting their winxp laptop to the network; guess what happend