The aims of this paper are the following ones: on the one hand, I study the new competitive forms that correspond to the development of the different markets linked to electronic platforms and social networks, on the web. On the other hand, I design a social welfare function to capture the positive and negative impacts produced by the development of these markets. In the first part, I will highlight the main social and economic changes caused by Internet Economy. I will show how the extension of market modified the production and the modalities of appropriating information. In a second part, I will design a social welfare function, and I will demonstrate why such markets dynamics are based on information asymmetries..