The goal of this research is to define and implement indicators for a Learning Management System (LMS). In particular, we focus on estimating patterns on the utilization of the message system by defining two quantities: the specific utilization and popularity. The idea is to take into account the perspective of academic institution managers and the administrators of the LMS, for example to understand if a particular department fails at providing a useful LMS service, or in order to allocate the correct amount of resources. These indicators have been tested on the LMS employed by the "Universita degli Studi di Milano-Bicocca" (Milan, Italy), and in general provided a picture of poor utilization of the message system, where the usage follows a pattern similar to the Zipf law. This feature, correlated with the principle of least effort, suggests that LMSs should join forces with existing social networking systems to create strong online learning communities.