In this paper, we discuss the impact of user's profiles on identity representations in web 2.0. We introduce a classification of 3 different types of identities: declarative identity, acting identity and calculated identity. This typology summarizes the theoretical model of "self-representation" in interactive devices, originally proposed in [Georges 2007]. "Declarative identity" (1) is constituted by data given by the user in the subscription process, and which he/she can subsequently modify (name, birthday, photograph etc.); "acting identity" (2) is constituted by data provided by the system relative to user actions (specific requests etc.); "calculated identity" (3) is constituted by numbers, calculated by the system, which appear in the user profile (number of friends, number of groups etc.). On the basis of a statistical analysis of Facebook data, we find that acting identity is much more valorised than the other two types. We discuss the philosophical implications of this trend of Computer Mediated Communication to valorise acting identity, which continuously draws from new interactions with the interface. As a consequence, we question if it is possible at all for a user to develop a consistent self-representation under such conditions.