koos@greenblatt:~$ host www.facebook.co ... / 2012-05-22

koos@greenblatt:~$ host www.facebook.com
www.facebook.com has address 69.63.189.70
www.facebook.com has IPv6 address 2a03:2880:2110:3f04:face:b00c::

Production IPv6 for a large-scale top100 site. Good for them. I'm still not joining!

I'm not sure whether this will cause loads of IPv6 traffic: all stylesheets and images come from static.ak.fbcdn.net which points to akamai:

koos@greenblatt:~$ host static.ak.fbcdn.net
static.ak.fbcdn.net is an alias for static.ak.facebook.com.edgesuite.net.
static.ak.facebook.com.edgesuite.net is an alias for a749.dsw4.akamai.net.
a749.dsw4.akamai.net has address 82.94.229.19
a749.dsw4.akamai.net has address 82.94.229.33

So it looks a bit retro on a V6-only connection until facebook gets ipv6-enabled on akamai.

Update 2012-05-29: Also noted by Derek Morr: Facebook vs. Google+ over IPv6 - Living with IPv6. Indeed, google+ works completely over IPv6 when connected to a network where the resolvers are in the Google IPv6 whitelist. According to a comment on that article the content delivery network used by facebook will add IPv6 support this week.

Second update 2012-05-29: Now fully IPv6 enabled:

koos@greenblatt:~$ host static.ak.fbcdn.net
static.ak.fbcdn.net is an alias for static.ak.facebook.com.edgesuite.net.
static.ak.facebook.com.edgesuite.net is an alias for a749.dsw4.akamai.net.
a749.dsw4.akamai.net has address 82.94.229.19
a749.dsw4.akamai.net has address 82.94.229.33
a749.dsw4.akamai.net has IPv6 address 2001:888:2000:37::525e:e513
a749.dsw4.akamai.net has IPv6 address 2001:888:2000:37::525e:e521

And indeed working as content delivery network: those IPv6 IPs are netwise close to me. Five hops with traceroute6.