Interesting characteristics of large-scale events are their spatial distribution, their extended duration over days, and the fact that they are set apart from daily life. The increasing pervasiveness of computational media encourages us to investigate such unexplored domains, especially when thinking of applications for spectator groups. Here we report of a field study on two groups of rally spectators who were equipped with multimedia phones, and we present a novel mobile group media application called mGroup that supports groups in creating and sharing experiences. Particularly, we look at the possibilities of and boundary conditions for computer applications posed by our findings on group identity and formation, group awareness and coordination, the meaningful construction of an event experience and its grounding in the event context, the shared context and discourses, protagonism and active spectatorship. Moreover, we aim at providing a new perspective on spectatorship at large sc...