This is an interesting book - Connected: Why Fat is Catching and Money is Contagious by Nicholas A Christakis and James H Fowler. It could have done with being about 50 -75 pages shorter as I felt the authors got a little carried away with the subject. It is all about social networks and the way they work. Some of the experiments which have been conducted in the past on this subject are relatively well known. There's the 6 degrees of separation - where people managed to send an e-mail to someone they didn't know by first of all sending it to someone they did now - on average it takes 6 people to make the chain to anyone in the world. Well anyone with an e-mail address. There's also the old trick of standing in the street and looking up at something on a building or in the sky and seeing how many people stop and do the same thing - works best if there are several of you.
But the book builds on this idea and covers all sorts of things such as the spread of sexually transmitted diseases among high school and university students; why so many people voted how they did in the last US Presidential election; how one person losing or gaining weight can influence others not immediately connected with them.
I found the chapter on American politics a shade confusing but the rest of the book was interesting and actually quite positive in outlook for the future of mankind. The one thing that struck me as most enlightening in the age of more and more government regulation was that co-operation between people flourished where there was less regulation. Hmmm - definitely food for thought there then!