This paper focuses on the extent to which online information sharing practice is socially motivated. A key interest is how knowledge of the existing social connections between actors may predict their information sharing behaviour when they move into an online environment, and the relative importance of these connections when set against other factors that may motivate online information sharing within a closed group. The examination of online information exchanges between members of a defined community of bloggers reveals that those with established off-line relationships are more likely to interact with one another when they move into an online environment than those who have not enjoyed earlier contact. The findings of the empirical study are evaluated with reference to social exchange theory, with acknowledgement of the importance of shared social capital as a prerequisite for the efficient operation of work-groups, both in face-to-face and online environments. It is concluded that social exchange theory can be deployed as a means of explaining online information sharing behaviours. The study findings have implications for the design of environments for purposes of online information sharing, especially in terms of the provision of substitutes for physical proximity in distributed organisations, the operation of reward systems, and expectations for communities to develop their own information sharing ecologies.