Following the approach initially proposed in Maury & Venel [30, 31], we consider here crowd motion from the standpoint of granular media, and we investigate how theoretical and numerical tools in non-smooth analysis can help better understanding some paradoxical features. We shall be especially interested in evacuation processes, jams, and we will detail how the granular nature of the flow helps to understand two well-known phenomena, the so-called " Faster is Slower " effect, and " Stop-and-Go " waves.