Not surprisingly, most of the article here is basically Dunbar saying that Facebook friends aren't *real* friends, so they don't count in the 150. The below is a nice little bit on changing interconnectedness dynamics though:
This isn’t to say that Facebook and its imitators aren’t performing an important, even revolutionary, task — namely, to keep us in touch with our existing friends.
Until relatively recently, almost everyone on earth lived in small, rural, densely interconnected communities, where our 150 friends all knew one another, and everyone’s 150 friends list was everyone else’s.
But the social and economic mobility of the past century has worn away at that interconnectedness. As we move around the country and across continents, we collect disparate pockets of friends, so that our list of 150 consists of a half-dozen subsets of people who barely know of one another’s existence, let alone interact.
Our ancestors knew the same people their entire lives; as we move around, though, we can lose touch with even our closest friends. Emotional closeness declines by around 15 percent a year in the absence of face-to-face contact, so that in five years someone can go from being an intimate acquaintance to the most distant outer layer of your 150 friends.
