In this paper we investigate the phenomenon of online social networking within organisations. While Internet Social Networking (ISN) as a public phenomenon has drawn considerable interest from the academic community, little knowledge exists about the potentials and modes of use of social networking sites (SNS) that emerge within organisations. We draw on three cases of SNS implementation and use in large, knowledge-intensive organisations. A cross-case analysis reveals a set of three modes of use of corporate SNS, which we discuss in light of existing literature on SNS use in the public sphere. More importantly, we reason on the open and flexible nature of these technologies and discuss implications for organisational implementation. Striking differences in the frequency of use and perceived role of SNS across the cases lead us to reason about the importance and ways of embedding open technologies with existing ICT-enabled work practices in the organisation by way of co- evolution of systems and their use.