I think the evidence in this post suggests that a real friendship needs to go beyond some curated communication system where some one else (or some algorithm) decides what you hear from each other. Otherwise you may miss significant events in each other's lives.
fb used to be a legitimate communication system - you could write on walls, you could poke, you could do a lot of stuff with fb apps that solicits an immediate response.
fb today is not the fb of 2007. I know a lot of users grew up with fb but fb did not grow up with us.