Even single NAT is not trivial when a few hundred thousands of active users are behind it, just because of the sheer scale. For a major part of the users "The

Even single NAT is not trivial when a few hundred thousands of active users are behind it, just because of the sheer scale. For a major part of the users "The Internet" == "The Web", and applications like Skype use any available transport including avian carriers, this limits the impact. But does having NAT increase the code complexity and increase the maintenance cost ? It does. So, I would treat it as a short-term high-interest loan. If you do not have other choice - sure, go for it. But if you can avoid it - you will avoid a couple of gray hairs too.