In this paper, we examine the question of how participants in online communities enact organising structures. We conduct an empirical study based on interpretative and quantitative data and analysis, and argue that communicative genres fulfil the role of intangible organising structures in online communities. These structures are important in the absence of more formal or tangible structures. Furthermore, we take into account participants' position in the social network and find that distinct participant clusters use communicative genres quite differently. In particular, we distinguish four participant clusters using distinct genre repertoires: team players, who make short, advising messages; storytellers, who post less but longer and very social messages; utility posters, who share knowledge but neglect social interaction; and all-round talents, who engage in various actions and have average messages, without blinking out in any activity. With this research, we provide an analytical tool that allows practitioners to assess community activities, and inform and evaluate strategies for change toward improved outcomes.