Facebook and other social networks promise an unlimited number of potential friends, but anthropologist Robin Dunbar spots a "fundamental flaw" in that logic: "Our minds." Humans are cable of having meaningful relationships with a maximum of about 150 people, whether they're online or off, writes Dunbar in the New York Times. "Yes, you can 'friend' 500, 1,000, even 5,000 people with your Facebook page, but all save the core 150 are mere voyeurs looking into your daily life."
That's not to say Facebook, et al, don't serve other useful networking roles. For one, they "allow us to keep up with friendships that would otherwise rapidly wither away." And maybe more importantly, they allow us to integrate "disconnected subsets of friends." Because of that, "we can rebuild, albeit virtually, the kind of old rural communities where everyone knew everyone else," writes Dunbar. "Welcome to the electronic village."