NYT:
Mr. Barabasi believes the human social network is scale-free with the expected smattering of richly connected hubs. Mr. Watts disagrees. “If you asked people to list the number of people they recognize, that could be scale-free, everyone recognizes Michael Jordan,” he said. “But if you said, `Who would you trust to look after your kids?’ That’s not scale-free. As you start to ratchet up the requirements for what it means to know someone, connections diminish.”