Social media technologies are making fast inroads into organisations. In the context of knowledge-intensive work the propositions of improved communication, information sharing and user involvement seem particularly promising. We study the phenomenon of Enterprise Social Networking (ESN) in the context of Professional Service Firms (PSF). Our case study investigates emerging knowledge work practices on the ESN platform Yammer within Deloitte Australia. We perform a genre analysis of communication data and uncover a set of emerging practices. We reflect on our results in the context of the knowledge-intensive nature of professional service work. We find that Yammer in the case company has become 1) an information-sharing channel, 2) a space for crowdsourcing ideas, 3) a place for finding expertise and solving problems and 4) a conversation medium for context and relationship building. We conclude by positioning ESN in the well-known 3-C model for classifying collaborative ICT.<br /
