The problem with Facebook's usefulness isn't that I find it useful, it's that everyone else in my circle finds it useful. This means that any event, major life change like marital engagements and announcements of expectancy or child birth, and general updates of wellbeing from my elderly family are all communicated via Facebook. For example, a friend of mine from high school recently had a child. I had not logged into Facebook for over a year, and suddenly found myself embarrassed for my lack of keeping up with her when I ran into her at the grocery store while she was chasing down a toddler who had escaped down an aisle. I did not have the slightest clue as to her family status, because I stopped logging into Facebook to receive those updates and she stopped going out to parties and bars where we normally would run into each other (to avoid drinking and cigarette smoking), and it just appeared like we drifted apart.
Even now, some friends of mine are planning a trip together, and it's entirely done within a closed group on Facebook. There is no way for me to participate in this trip without maintaining some status on Facebook, else my significant other will have to just relay all that information, which is tiring, and prone to the "telephone" effect.