This paper investigates the impact of social media interactions on the use context of enterprise systems (ES) at a global telecommunications company based in Europe. We conducted a detailed field study of users in three countries who execute tasks collectively using social media capabilities within their ES. The findings provide rich insights into these social media interactions, their influence on ES users' sense of 'presence' and their impact on the completion of tasks. Our key research contribution is to introduce the idea of 'virtual co-presence' as a means of understanding the digitally mediated presence of ES users. In addition, we demonstrate how virtual co-presence and the relationships afforded by social media shape ES users' interactions and collective completion of tasks in a dispersed work context. Drawing on the insights gained from the effect of virtual co-presence on ES users, the paper outlines some implications for the theory and practice of collective work in ES use.