I modified both /etc/hosts and /private/etc/hosts here it is
##
# Host Database
#
# localhost is used to configure the loopback interface
# when the system is booting. Do not change this entry.
##
127.0.0.1 localhost
255.255.255.255 broadcasthost
::1 localhost
fe80::1%lo0 localhost
0.0.0.0 www.facebook.com
0.0.0.0 facebook.com
0.0.0.0 login.facebook.com
0.0.0.0 www.login.facebook.com
0.0.0.0 fbcdn.net
0.0.0.0 www.fbcdn.net
0.0.0.0 fbcdn.com
0.0.0.0 www.fbcdn.com
0.0.0.0 static.ak.fbcdn.net
0.0.0.0 static.ak.connect.facebook.com
0.0.0.0 connect.facebook.net
0.0.0.0 www.connect.facebook.net
0.0.0.0 apps.facebook.com
Apparently firefox still can connect to facebook, but apparently a ping facebook.com times out as expected. I even restarted firefox without success.
I've also ran
dscacheutil -flushcache;sudo killall -HUP mDNSResponder
Any idea ?