This paper tackles with the background theory and the typology of incentives that characterize behavior in online social interactions. Online social interactions are the major element of activity in online communities. Social network theory and in particular the strength of weak ties hypothesis can provide an analytical framework for studying them. We contribute by introducing a typology of social, behavioral and economic incentives by formulating related hypothesis. We then combine these hypothesis in a proposed structural model from which we theorize the different classes depending on the model configuration