I have a lot of Facebook friends that I would completely lose touch with, because I have no backup contact info. If I knew ahead of time that Facebook was going away, I could procure a backup method but if Facebook just disappeared one day, I would have little chance of contacting a number of acquaintances and former colleagues. In the past, I probably would have had a Rolodex, a collection of business cards or even a local phone book to fall back on, but Facebook has pretty much replaced all of that. Even though I have mainly stopped browsing timelines, this is the main value of Fb now for me.