There are a couple of old and dear friends that I used to hang out with regularly in my 20s, who are now dispersed in various locations, with whom my only connection is Facebook, because we all live too far away to just drop in on each other anymore. If we were to inadvertently lose contact, I think all of us would go out of our way to try to reestablish some connection, even if it took a few weeks or months to accomplish. So there are 2, maybe 3 of those.
But, in terms of people I actually see or talk to on a regular basis, there are none.