The post is worth checking out:
We measured the extent to which your friends’ behavior predicts your own, and found that in several consumer domains the effect is substantial, complementing traditional demographic and behavioral predictors.
That friends are similar along a variety of dimensions is a long-observed empirical regularity—a pattern sociologists call homophily. As McPherson et al. write in their canonical review on the subject, “homophily limits people’s social worlds in a way that has powerful implications for the information they receive, the attitudes they form, and the interactions they experience.” Turning this statement around, where there is homophily, one can in principle predict an individual’s behavior based on the attributes and actions of his or her associates.
I put this figure here because it looks cool.