Back when I worked at RCN in 1999, they had begun putting cable modem
customers behind NAT using 10/8 addresses. This occasionally drew
complaints from customers who were expecting a public IP (probably
wanted to host a server), but they weren't given much choice. Whether
or not they're still NATing, I have no idea.
I can see the benefits for residential services like cable modem or even
dial-up when there will never be a need for multihoming. Practically
unlimited IP pool, and I assume it's easier to control things like worm
propogation (correct me if I'm wrong). However, I'm sure there's
several compromises you'd have to make in order to operate this way.
-Rob