The Wall Street Journal's "numbers guy," Carl Bialik, zoomed in on that number – 150 – which many reporters have cited as the limit to the number of personal contacts any human being could possibly sustain. This is when they're writing stories about the lengthy friends lists some teens have amassed in social sites. The 150 comes from the research of Robin Dunbar at Oxford University, "extrapolating from social groups in nonhuman primates and then crediting people with greater capacity because of our larger neocortex, the part of the brain used for conscious thought and language." Ah, got it. So we definitely can sustain more friendships than primates. But, actually, Dunbar himself, Bialik reports, believes that social sites "could 'in principle' allow users to push past the limit." To the professor, the real question is "whether those who keep ties to hundreds of people do so to the detriment of their closest relationships – defined by Prof. Dunbar as those formed with people you turn to when in severe distress." Bialik cites another recent UK survey that found – no huge surprise – friendships really start offline, but "less-close friendships and acquaintanceships, however, also die offline, while the Web can help sustain them" [read the article for examples]. I suspect this is one of the things youth who move far away, go off to college, or graduate and leave behind college friends so appreciate about social networking. There's much more that's thought-provoking in the Journal column – do check it out.