Facebook connections ensure that your account is easily retrievable if anything ever happens to your Forest. It also ensures that you can login to any device with your Facebook without worrying about transferring games. But you should always make sure to note down your unique user ID, as support are not able to find missing games via Facebook name.
By connecting to Facebook, you will be able to access exclusive in-game content!
Creating an account also lets you send Gifts to your Facebook friends, who already play, and be part of the wider community of players.