Nicholas Christakis: The Hidden Influence of Social Networks

This is fascinating:

It's 18 minutes long, but like a lot of TED Talks, it's interesting as all hell. The speaker turned his experience working in hospice care to study how common human conditions spread through social networks. Not only does he talk about emotions like happiness and anger (and how those feelings seem to have a life beyond the individual expression of them) but obesity as well.

One thing I wish he'd addressed (and I'm almost tempted to write him a letter to ask him about...