Malcolm Gladwell, with his inimitable instinct for picking interesting topics, has an article in The New Yorker (http://www.newyorker.com/reporting/2010/10/04/101004fa_fact_gladwell?currentPage=all, publication date October 4, 2010) focused on the nature of social activism, and the role of social network communication in fostering (or not) activism. Citing bloggers and chatterers who champion the role of social media in various recent social movements, Gladwell makes the important distinction between friendship and “weak ties”, such as those created on Facebook and Twitter. The social media sites help manage acquaintances or former friends, or people you are interested in, but not necessarily people with whom you might engage in a difficult or risky behavior such as social activism. Nicholas Christakis and his colleagues have addressed the nature of “Facebook friendship” in working with Facebook data; although many people had 1,000 or more Facebook “friends”, it seemed clear that all these were not friends in the sense of shared activities, much less activism. Christakis et al. developed a proxy for “real friends” on Facebook: people who appear in a Facebook picture with you. By this measure, Facebook members have about 6.5 “real friends” (the 0.5 friend is not a dog). Christakis discusses this work in a recent TEDx talk, available at http://www.youtube.com/watch?v=VQEf-JyBnZ0. Coming back to Gladwell, he makes the (appropriate) point that social media-based networks are good for things that require retrieving information or low-effort, low-value actions, but not coordinated efforts such as social activism. Gladwell’s arguments are sound from my point of view, but he doesn’t dig deeply enough. For example, in citing Granovetter’s pioneering work on the “strength of weak ties”, he doesn’t delve into more recent work, such as Damon Centola’s experiments cited in our blog (September 7), which suggest that such weak ties may be less relevant in behaviors which depend on complex contagion (which may be many human behaviors). And he doesn’t address the power of “naturally occurring” social networks, such as those mapped by MedNetworks, to foster behavioral change, or in “created” social networks, again like those MedNetworks can develop, to change important health behaviors such as smoking, etc. Social network technology can change the world, or at least a small part of it, but it requires a systematic, data-based approach.