Is change social? Well, yes.

Nice article on research that shows how Quitting smoking travels (like practically everything else) through social networks of people who know each other.

http://socialmediatrader.com/smoking-and-social-networks

P.S. We keep being surprised by this kind of research, but the insight goes right back to the very start of diffusion research... a simply written, plain English, article written by Bryce Ryan and Neal Gross in a humble rural sociology journal in 1943...

To see it, go to http://chla.library.cornell.edu then search under "diffusion" with the author names "Ryan" and "Gross". Their article is in Rural Sociology Volume 8.