This work sets the theoretical stage for future empirical investigations of the socio-economic dynamics in virtual social networks (VSN), at member and network entrepreneur levels. In so doing, I start by identifying the empirical loci, Flickr and LinkedIn, justify and describe the choices. A model of the utility function of the generic VSN member is followed by descriptions of the value dynamics for each VSN, which in turn create the premise for an economic model of VSN as platforms for multi-sided markets. The model is built by considering several theoretical angles from the perspectives of microeconomics and sociology of networks. The contribution is in extending theoretical and empirical insights across disciplines and fields with the idea of exploring and understanding the emerging VSN-phenomenon.