The Dunbar no. & online social networks

A few years ago, extrapolating from her study of primates, Oxford Unviersity-based anthropologist Robin Dunbar theorized that "the size of the human brain allows stable networks of about 148," The Economist reports. That's usually rounded off to 150 and called "the Dunbar number." The Economist interviewed Facebook's "in-house sociologist," Cameron Marlow, whose findings pretty much match up with the Dunbar number - an average of around 120 "friends," but ranging from a handful to thousands. I've long suspected that people whose friend lists are at the upper end of the spectrum are marketing more than being friends or, in the case of young adolescents, working through the "popularity contest" that school social scenes can represent. Here's the thing, though: Marlow told The Economist that the average person with 120 Facebook friends responds to the comments of (keeps in close touch with) only 7-10 friends (men at the low end of that range) - their "core network." Beyond that are the "casual contacts that people track more passively." The Economist ends with the observation that "humans may be advertising themselves more efficiently. But they still have the same small circles of intimacy as ever." Not that everybody uses social network sites to advertise themselves, but I do think the second half of that observation is exactly right. [See also the UK's NewScientist.com on "how social networking might change the world."]