Emergence and resilience of social networks: a general theoretical   framework
  We introduce and study a general model of social network formation and evolution based on the concept of preferential link formation between similar nodes and increased similarity between connected nodes. The model is studied numerically and analytically for three definitions of similarity. In common with real-world social networks, we find coexistence of high and low connectivity phases and history dependence. We suggest that the positive feedback between linking and similarity which is responsible for the model's behaviour is also an important mechanism in real social networks. 
George C.M.A. Ehrhardt, Matteo Marsili, Fernando Vega-Redondo