You are communicating with your friend, but instead of talking directly, you write a note, hand it to Mr. Facebook, who opens it, reads it, then closes it and hands it to your friend, who in turn writes back, handing it to Mr. Facebook first. That’s more how communication happens on FB. FB acts as the mediator of the communication, a middle man whom both of you interact with to have the conversation. They are not spying from afar—you are directly giving them your communications.