First of all, everything on FB is as public as the poster decides to make it. If you put in a tiny amount of effort, you can separate your friends into groups

First of all, everything on FB is as public as the poster decides to make it. If you put in a tiny amount of effort, you can separate your friends into groups and have your posts by default only visible by a selected group of friends. (Funny thing is that when Google came out with circles for G+, the people who raved about it never realized the same feature was available at FB for ages. Granted, the circle metaphor and UI made the feature easier to use in G+, but the functionality was always there at FB). Really, the only privacy issue with FB is controlling what other people post about you (i.e., your friend takes a picture of you and posts it to their friends). Secondly, I don't think anyone has claimed that they maintain a deep relationship using FB only. Like I mention in a nearby reply, having the constant superficial connection through FB strengthens the actual time spent together.