You will only see your neighbors on the progression path if their games are Facebook-connected. Neighbors will be represented by their profile picture, and their position on the progression path will indicate their level.
The visibility of Facebook Friends is exclusively controlled by Facebook, and some friends may not always be visible. This is particularly likely if someone has not logged into the game for an extended period of time.
The visibility of Facebook Friends is exclusively controlled by Facebook, and some friends may not always be visible. This is particularly likely if someone has not logged into the game for an extended period of time.