It also means that collecting data based on your IP is not an invasion of privacy. With IPv6 there is the potential for much finer grained assignment of IP addresses to such an extent that an IP address could become uniquely identified with an individual more readily than today.
It is not currently possible with the underlying routing technologies, nor do I think it would be desirable, for you to get a single IPv6 address assigned to your device for the entirety of its lifetime.
Firstly, each publicly route-able address (for both IPv4 and IPv6) belongs to a particular network (known as an Autonomous System). The traceroute utility on unix and windows can be used to show you the path from your local network to a particular network, simply by traceroute'ing address that you know are operated by a particular network.
The way this works is a series of routing protocols that ask the question, "Which network routes this address and what is the best path to get there?" and answer it in various ways.
So, I do not think it is possible or desirable for a single publicly route-able IPv6 address to follow a particular device between networks.
Finally, I would like to point out that, even though we can change them, MAC addresses are supposed to be the permanent unique identifier for a particular network interface. I do not think adding an IP equivalent makes any sense, especially when a particular interface may have multiple IP addresses, and a particular machine may have multiple interfaces.
Now I will forget my hackernews password once again, until I am needed.
Not unless they decide to completely revamp how addresses are assigned, no.
Edit: and to address the comment that slipped in just ahead of me...MAC addresses as a part of IPv6 addresses are fine. If the interface is on several subnets, then the network portion of the IP address will be different.
Edit2: To clarify my initial comment, as the other commenter stated, there is no effective way to handle the routing for keeping the network portion the same, so that would always depend upon where you are. The only possibility could be to be assigned a permanent host ID, but considering how many devices the average person has with network access (I have a couple dozen easily, but I'm not average,) I'd think that this would be impractical anyway.
It also means that collecting data based on your IP is not an invasion of privacy. With IPv6 there is the potential for much finer grained assignment of IP addresses to such an extent that an IP address could become uniquely identified with an individual more readily than today.