The thing that I most enjoy about FaceBook is being able to chat in real time. There are friends & relatives that I wouldn't actually pick up a phone to call, but if I see them already online sometimes I'll pop in to say hi.
Earlier tonight I said hello to a friend in Colorado and we made plans for her to come and spend the weekend with me in May. (Coincidentally, she was the first person I ever met with MS, back before I was dxd.)
And yes, FB does keep tabs on your whereabouts. When I first returned from a trip to Israel, all the ads were written in Farsi!!!