Jonah Lehrer uses Mark Granovetter’s 1973 paper, “The Strength of Weak Ties," to rebut Gladwell:
Granovetter ... [argues] that weak ties play a seminal role in building trust among a large group of loosely affiliated members, which is essential for rallying behind a cause. ... While Gladwell argues that the flat hierarchies of online networks are a detriment to effective activism he cites the leaderless P.L.O. as an example Granovetter points out that leaders of social movements often depend on weak ties to maintain loyalty. He notes that organizations dominated by strong ties tend to produce fragmentation and cliquishness, which quickly leads to the breakdown of trust. This suggests that part of the reason Martin Luther King was able to inspire such discipline among a relatively large group of followers was that he cultivated a large number of weak ties.