Facebook seems to be at times a place where the sociopath and narcissist come to play. A perfect venue it gives them a place to put on a mask and pretend to be what they aren’t. Classically they will befriend someone that is lonely or has a deep need to be wanted, needed and accepted. The sociopath will feed on this need and make that person feel important to them. Almost a parental figure or a loving friend or significant other. They reel them in and when that person is hooked they take whatever is most important to them whether it be monetary or the physical need to be needed. When the time is ripe they strike. Sociopaths lack empathy and the capacity to feel much of anything so in order to get their thrills they attack, malign and try to destroy their victim. It is a game. Be very careful of those that seem to want so badly to be your friend or confidant as information given in the strictest confidence can then be used as extortion.
The narcissist on the other hand looks to be the center of attention at all times. They see no one but themselves.
Sadly people are taken in every day. Reputations ruined because of bullying posts and lies, hearts broken when the friend is no longer there but attacking on a daily basis. Do not allow yourself and others to be drawn in by these types.