Stable Community Structures and Social Exclusion

In this paper we study social exclusion in social (information) networks using a game-theoretic approach, and study the stability of a certain class community structures that are a Nash equilibrium. The main result of our analysis shows that all stable community structures (Nash equilibria) in this class are community structures under which some agents are socially excluded, and do not belong to any of the communities. This result is quite striking as it suggests that social exclusion might be the "norm" (an expected outcome) in social networks, rather than an anomaly.