The residential users don't need to have a globaly unique IP address.
That's like saying residential telephone users don't need to have a phone number at which they can be reached. (after all, the purpose of their residential phones is to call businesses for the purpose of obtaining services, right?)
There are lots of apps that would be valuable to residential users if residential users had reachable IP addresses. check the status of your alarm system, or your roast in the oven, or your freezer's inventory. Grab a picture from your baby-cam while you're out for dinner and have left the kid with the baby sitter. Reset the thermostat if you're going to be out of town longer than you thought. Do all of these from your portable phone/PDA which is running guess what? -- IPv6.
Also, don't assume that IPv6 addresses will be used by people or their personal computers. IPv6 enables lots and lots of individually addressable devices which don't have to be associated with individuals. Every km of highway can have an addressable traffic sensor so that police and emergency crews know exactly when and where a traffic accident happened. Every streetlight can be monitored to see if it is functioning properly or if it needs service. Every traffic signal can be made individually controllable so that they can dynamically adapt to changes in traffic patterns. For reasons like this, the demand for IPv6 addresses won't be determined by some linear multiple of the number of humans on the planet.
Finally, don't assume that IPv6 devices will require the support burdens we associate with PCs. PCs as we currently know them are dinosaurs. Appliances that talk to the network aren't going to need the same kind of technical hand-holding that PCs do (because they'd never succeed if they did), and neither will the devices that replace what we now think of as personal computers.
IPv6 will eventually replace IPv4, but it's misleading to think of IPv6 as just a replacement for IPv4. By the time IPv6 replaces IPv4, we won't recognize the IPv6 network as something that resembles what the IPv4 network is used for today. Even though the underlying technology is very similar, IPv6 is really a new kind of network, one that enables things that were really never possible with IPv4 on a large scale.