Majorities, reach, repercussions Definitively, rapidity whereupon Internet have propagated is extraordinary in a globalised world very active, and that through her, already there are distances no not to be found out the world-wide events that they occur in the countries that compose this planet Earth and to communicate to us with different people who live in distant countries to ours. It is perceived like every time, one occurs to the birth and reaffirmation of the relevance of the social networks in topics that involves common interests, friendship, relations, interchanges among others, obtaining until the moment a great height that cannot be ignored. It is known and it remembers Wikipedia to us, that a social network is a social structure composed of people (either organizations or other organizations), who are connected by one or several types of relations, such as friendship, kinship, I interest common, economic interchanges, sexual relations, or that share beliefs, knowledge or prestige. Tmese in account, that the social network analysis has been used in epidemiology in order to help to understand how the landlords of human contact favor or prevent the propagation of diseases like HIV in a population. The evolution of the social networks sometimes can be simulated by the use of models based on agents, providing information on the interaction between the communication norms, propagation of rumors and the social structure. The social network analysis also can be an effective tool for the massive monitoring – for example, the Information Total Awareness Information Awareness realised a thorough investigation on the strategies to analyze the social networks to determine if the EE.UU citizens were or political nonthreats. The theory of Diffusion of innovations explores the social networks and their roll in the influence of the diffusion of new ideas and practices. The change in the agents and the opinion of the leader often has a more important paper in the stimulus to the adoption of innovations, although also inherent factors to the innovations take part Very interesting when one comments in addition, that social network analyses study this social structure applying the Graph theory and identifying the organizations like " nodos" or " vrtices" and the relations like " enlaces" or " aristas".