NAT is only evil if you are a Google, a Government, or some other entity who is effectively prevented from monitoring someone because they do not have a unique IP address. NAT is the most effective privacy tool on the Internet. The only people calling it evil are ILECs, doubleclicks, and spies.
Of course NAT is also good when you want to switch Internet providers, or have more than one ISP. Without it you would have to renumber all your internal hosts to change or fail-over. ILECs have so far blocked NAT in IPv6 because it will provide such good vendor lock-in.
NAT is also incredibly effective in firewalling outside hosts from getting a free pass to internal networks. Of course spies, "aggregators", and spyware vendors don't like this.
The sad part is that few will adopt IPv6 until it has a standardized NAT. ILECs don't really care if this never happens because they will make a bundle reselling addresses in the resulting IPv4 bubble. Not just ILECs of course, but companies like Cisco, HP, and even Allstate Insurance who registered millions of IP addresses decades ago, before the advent of CIDR.
I guess all this is not really so sad when you consider that what's really sad is our (US) government, who can't even see what's coming down the pike.
