I’ll add one thing to your list:
We are not supposed to remain friends forever with everyone we’ve ever known or met! Do you need to be Facebook friends with the girl that sat in the front row of your 6th grade class even though you haven’t seen her since 6th grade? Or your brother’s old girlfriend from 6 years ago? Or your hairdresser? Or the neighbor who moved across the country 10 years ago and whom you haven’t seen or spoken to since? Or the guy who sold you your car? Are these people really your friends? Of course not!
Once you have a friend on Facebook, you feel obligated to keep them a friend forever. It’s considered rude to unfriend someone so you hang on to them, pretending they matter to you when they don’t and shouldn’t because they are really aren’t a part of your life or because they are not an important part of your life.
People are supposed to come and go in our lives. If we are clinging to old meaningless relationships by spending hours following people on Facebook who we really don’t know or care about, how will we have time for the authentic relationships in our lives right now?