Abstract : This research within La Poste's DSIC is focused on corporate reputation and on e-reputation through the prism of information and communication sciences. It proposes the development of a web monitoring and a social search process enabling to assess, manage and build online reputation. At first, we present a theoretical framework for corporate reputation as an info-communicational object. Then we discuss corporate e-reputation such as a strategic information made up of all commensuration indicators constituted by intentional (endogenous or not) interactions with the virtual communities and the firm : productions of opinions, assessment or public behavior. In a second step, we investigate how La Poste group can build its e-reputation. By "build" we mean the way to structure the informational environment where customers evolve each day on social web, and more specifically on the Twitter platform. In this context, our empirical observations allow us to highlight, question and analyze, web users whose informational practices permit us to qualify of "facilitators-agents", and whose main characteristic is to participate in informational prescription and the documentary mediation on the web. After the observation of some of these agents and the production of a typology, we propose a model and a monitoring process to integrate them. Our process's results in La Poste show the need to take into account and analyse recommendation practices on social networks to build corporate e-reputation proactively.