This is a nice talk by Nicholas Christakis on Sociology and Social Networks. It is very concise and well presented covering a quite broad range of topics such as suicide, social capital, collective behavior and social networks.
What attracted my attention though was the part on the Social Network Effect Behind Obesity, where Christakis talks about this paper he and James H. Fowler have published in The New England Journal of Medicine (in the video, skip to 19:06). Quite impressive!
