Our on-line students, being mainly busy worker-students, study almost alone. To improve their interaction we use asynchronous tools (Wiki or forums), but we notice that interaction becomes high mainly when the discussion is focused on a task to be graded for the exam or when the teacher/tutor is very active in the community. We present SOCIALX, our exercise sharing tool, an application to e-learning of a simple reputation system to increase the student motivation and interaction, and to let them learning from each other, either by reusing other's solutions or by correcting other's mistakes. Moreover, students gain reputation from others reusing their solutions. In this we want to engage students in learning activities at the highest cognitive levels of the Bloom taxonomy.