Open Source Software (OSS) has received wide attention from the research community, analyzing both the innovation process of software development by distributed and unrelated teams, and the market dynamics at play between free" and proprietary software. Up until now, OSS adoption has been irregular, although it seems to be breaking the dominance of existing players in some market segments. In this paper, we contend that due to the particularities of its development process, traditional ways of explaining IT adoption -rational decision making, technology diffusion models, and the psychology of the decision maker-are insufficient to explain the case of OSS diffusion. We believe that the existence of a strong and diffused development community leads to a new role of the user community, as both are intertwined. In addition, new concerns for social corporate responsibility and welfare create a new context, in which user gangs" may exert some degrees of pressure on the IT decision maker. Through the analysis of some significant cases we depict under which conditions significant OSS adoption may unfold, showing that in two of the cases studied user gangs play a significant role. The resulting preliminary framework will inform future work, in which we aim at validating the emerging insights gained in this research.