Did not exist.
Will never exist.
There was quite a lot of buzz about privacy with that new IPv6 thingy. Some say it is bad, as you will have a static address. Some say the privacy extensions will fix everything. I say: lemme rant ;)
First of all, that was the internet, when I started using it back in 1999:
[© New Yorker Magazine, March 1993] On the Internet nobody knows that you are a dog'
And that's the internet today:
Well, I'd say that's not correct. Even in 1999 facebook could know you are a dog (if you ignore the fact, that there was no facebook in 1999), it's just noone really cared about it. But let's start from the beginning :)
An IP-address is a 32-bit integer
An IP-address is technically a 32-bit integer, formatted into 4 8-bit parts (you can read more about IPv4 at Wikipedia), which makes a total of 4,294,967,296 possible IP-addresses. Your ISP has a range in this "address-space" it can give to its customers (you). My ISP (Unitymedia) "owns" about 300,000 IP-addresses (based on the RIPE database), which is about 0.007% of the whole address-space. If you look at the RIPE page, you see two common netname prefixes (DE-KNRW and DE-IESY-HFC) which match two regions of Germany where my ISP has its customers (Unitymedia is a merge of ish and iesy). What does that mean? It means one can map a Unitymedia customer into one of these regions, even if he would change his IP-address (Unitymedia uses DHCP with high lease-times, so this does not happen actually). It does not map the customer to a dog yet, but I bet real GeoIP databases can map them correctly to a city (I didn't try much, but this site suggests it works: http://www.ip-adress.com/?lc=en - at least they map me correctly to Duesseldorf).
Dynamic IP-addresses do not improve privacy
Given the above facts, even if Unitymedia would give me a new IP-address every X hours (many DSL-providers have X=24), it is still possible to map me into a set of about 150,000 "users" (here user means customer, there still may be multiple computers connected via the same line). I would even go further and say the set is much smaller, as I think I am not able to get every "free" IP-address from DE-KNRW-*, as these should be bound to cities/regions (GeoIP databases exist, you rememember?) and I do not move with my line.
Routers and reverse DNS kill privacy
Currently, "my" IP-address is 22.214.171.124, which has a reverse DNS entry ip-62-143-232-104.unitymediagroup.de and does not say anything about me or my location, besides of the obvious "Unitymedia customer". But look at the traceroute:
4 7111A-MX960-01-ae5.frankfurt.unity-media.net (126.96.36.199) 5 13NOC-MX960-01-ae8.kerpen.unity-media.net (188.8.131.52) 6 1411G-MX960-01-ae9.neuss.unity-media.net (184.108.40.206) 7 1411J-MX960-01-ae1.bilk.unity-media.net (220.127.116.11) 8 PH-1411J-uBR10k-06-Te-1-2-0.bilk.unity-media.net (18.104.22.168)
Frankfurt is about 250km from here, Kerpen about 60, Neuss about 10 and Bilk is a part of the city I live in, about 4km away from my home. I guess you get the idea :)
Browsers kill privacy too
Do I have to say more than a link to https://panopticlick.eff.org/? My Chromium scores one in 1,400,000. How much IP-addresses did I have to hide in again?
We are at the dog level now, dogs use BoneOS with FireBark, not Linux with Chromium :)
IPv6 kills cute kittens
Oh, and privacy, because with IPv6, there are 2^128 IPv6-addresses out there, of which your provider will maybe own a /32 (2^96 addresses) and give you a /48 (2^80 addresses) or (more likely) /64 (2^64 addresses). Then you enable the great IPv6 privacy extensions (RFC4941) and happily hide in your own assigned subnet, still being a customer of your ISP, still living in the same city and using your old browser... It's just about mapping subnets instead of individual IP-addresses then. And we can't get lower as the dog level
People can annoy me
I did not write all this to teach you, you can do yourself with Wikipedia and RFCs. There is a person out there, who thinks using a random name, mail address and twitter account could fool me into thinking that's a new, yet unknown, person to me. Well, I am not stupid, sorry. When you comment on my blog, your IP-address is logged, when I approve the comment, I often look at the reverse DNS and the whois entry of that IP-address (sorry, I AM paranoid). I even might check my webserver logs (or Piwik) where did you come from (Google etc), writing "accidentally" in your comment does not help :) Also, if you are trying to fool me, don't use your own computer, running Windows 7 and Firefox which I installed. Oh, and probably do not use your home line which I used to login into my admin-area using my unique Chromium ;)
Sorry Hanna Lena, the chicken has just eaten her own eggs...
And yes, one can track down a single person on this big thing called internet, IPv6 will not change this (in any direction).