Facebook not running IPv4 at all?
Nonsense. They have to run it somewhere or most of the victims wouldn't be able to connect!
How many phones & tablets actually connect via IP6?
How many broadband ISPs fully support IP6?
PING star-mini.c10r.facebook.com (18.104.22.168) 56(84) bytes of data.
64 bytes from edge-star-mini-shv-01-dub4.facebook.com (22.214.171.124): icmp_seq=1 ttl=55 time=11.6 ms