Why is there a Facebook icon next to some of my friends?
In the past, players could connect their game account to Facebook to use their Facebook profile photo and add Facebook friends. This is no longer needed thanks to the new and improved Friends Center.
The Facebook icon next to a friend’s avatar means you originally added them as a Facebook friend back when Facebook connection was available.
Also, if you previously connected your account to Facebook, you may still see your Facebook profile picture suggested as your in-game avatar.