The Social Contagion Hypothesis: Comment on "Social Contagion Theory:   Examining Dynamic Social Networks and Human Behavior"
  I reflect on the statistical methods of the Christakis-Fowler studies on network-based contagion of traits by checking the sensitivity of these kinds of results to various alternate specifications and generative mechanisms. Despite the honest efforts of all involved, I remain pessimistic about establishing whether binary health outcomes or product adoptions are contagious if the evidence comes from simultaneously observed data. 
A.C. Thomas
stat.AP