I don't know how I managed to forget this, but today is World IPv6 Day. What this means is some of the major players have switched on IPv6 properly, disabling any white listing or any other means they have to stop it breaking the Internet for people who are not ready for IPv6.
What does this mean for most people? Nothing, unless Facebook has stopped working for you.
What does this mean for people who care and know what IPv6 means? Connections to Google and Facebook (amongst others) should be done over IPv6 connections. A quick netstat and a few reverse lookups are showing that it is working for me. About a third of all current TCP connections from the machine I am writing this post from right now are IPv6. It's a good step in the right direction.
