In this paper, we analyse the role of the student's digital reputation as a motivational factor for successfully completing Massive Open Online Courses (MOOCs). After a review of the academic literature on the role that the student's reputation plays in community learning and to understand the role of involving the student that new techniques of gamification have taken in virtual learning, an empirical analysis is performed on the basis of data from a pioneer MOOC of Social Entrepreneurship (5016 registered students, 3250 of whom actually started). Using Classification and Regression Trees (CARTs) and Principal Component Analysis (PCA), we conclude that social reputation is a key factor for the student in successfully completing the course, and that the student's retention is, along with his e-reputation ("karma"), directly related to his degree of participation, the rewards received, and his correspondence with peers. This shows that one of the factors that explain the student's MOOC completion is his degree of interaction with other students, and particularly his reputation among them.