It seems that Google's IPv6 geo location database isn't as clean as it needs to be and this has caused my family some grief over the last few weeks. I run dual stack at home and I run both my wired and wireless networks at home with IPv4 and IPv6. My older daughter just returned home from college and fired up her laptop and when she attempts to go to http://www.google.com she is redirected to http://www.google.com.tw which she found rather alarming. In addition, all her searches and links were coming back with Chinese characters and links obviously due to this. This seems to affect YouTube and all other Google services also.
Turns out the IPv6 tunnel broker I use from Hurricane Electric has assigned me out an IPv6 prefix from their Fremont 2 facility and for some odd reason the prefix is being tagged by Google as being located in Taiwan. This is the reason that the web request is being redirected to the .tw domain instead of the regular .com domain.
This isn't a huge deal for me as I can make tweaks to my daughter's laptop and fix the issue. For many others who may start to be provided IPv6 addresses as part of a nationwide rollout for their ISP this could be a HUGE problem. Granted, you would hope that Google would work with local service providers to keep that database relatively accurate but it seems Google hasn't yet responded to Hurricane's requests to fix it even though Hurricane has provided them with a full accounting of their IPv6 prefix locations (or it is my understanding that they have provided it.)
If you have problems with your IPv6 prefix not being properly geo located with Google you can submit your information at this link and see if it is fixed. A quick warning, the form doesn't take the /64 prefix portion, just the address so leave the prefix off. As a side note, this submission form works for IPv4 too.