end-user machines only initiate TCP sessions; they don't listen for them
That's not a misfeature of NAT -- it's adjustable at the router/firewall. Games, chat, etc. work perfectly well given the appropriate configuration of your router.
We're talking about networks which have been assigned private-network (RFC 1918) addresses due to IPv4 address exhaustion and ISP market segmentation — but which gateway onto the public network via NAT and expect to access public-network resources.
Correct, except for the reasons why they were assigned private-network addresses. In the networks I'm familiar with the machines were assigned RFC 1918 addresses because it's convenient (there's local control over IP assignment), because the network has to deal with machines coming and going (laptops, smartphones), and because many of these machines are not supposed to be accessible from the pubic internet.
These are not secured from the public network
Sure they are. That is, some of them are, provided the local sysadmin made it so.
To give a trivial example, consider a local database server which does not run any browsers and which responds to (and is supposed to only respond to) just local machines -- easily done if the local machines use private-network IP addresses which are not routable over the general internet.
If all hosts are distinguishable by address, then the security-sensitive service can accept traffic from a good client and reject traffic from a bad one.
That's a very naive approach. IPv6 is not an immutable GUID given to a piece of hardware once and forever. A MAC address is something close to that and even then it's trivially spoofed.
Consider a scenario where I'm cloning VMs at a rate of, say, one per second and each lives for a couple of minutes. What will your "money-making web server" do about them?
Correct, except for the reasons why they were assigned private-network addresses.
In the case of end-user networks, the reason is simple: end-user ISPs issued only one IPv4 address per customer, under the assumption that the customer would attach only one host to the network. This assumption was sometimes tacit, but sometimes explicit as a matter of contract or support policy. It became increasingly inappropriate for broadband users' actual use.
Customers worked around this by deploying NAT devices. This was sometimes against the ISP's wishes — to the ext...
At LW London last week, someone mentioned the possibility of a Google Glass app doing face recognition on people. If you've met someone before, it tells you their name, how you know them, etc. Someone else mentioned that this could reduce the social capital of people who are already good at this.
A third person said that something similar happened when Facebook started telling everyone when everyone else's birthday was. Previously he got points by making an effort to remember, but those points are no longer available.
Are there other social skills that technology has made obsolete? And the reverse question that it only just occured to me to ask, are there social skills that are only useful because of technology?
I'm not really sure what sorts of things I'm looking for here. "Ability to ask for directions" seems like one example, but it feels kind of noncentral to me, I don't know why. But I'm mostly just curious.