Jonah Lehrer pores over the research by Nicholas Christakis and James Fowler on social networks and obesity:
It turns out that the old warning of David Hume - causation is a slippery concept and a tricky thing to prove - is even more relevant in the age of excess data, when supercomputers can sift through terabytes of social information and uncover all sorts of fallacious correlations. Christakis and Fowler get around this problem through some clever analytics: they show, for instance, that obesity is much more contagious between close friends than it is between acquaintances, which suggests that social networks are the driving mechanism (and that the new neighborhood McDonald's isn't). Regardless, it will be interesting to watch this new field evolve in the next few years, as the Humean skeptics do battle with the enthusiastic believers...