The link above points to the manuscript of:
Hall, H., Widen, G. & Paterson, L. (2010). Not what you know, nor who you know, but who you know already: examining online information sharing behaviours through the lens of social exchange theory. Libri, 60, 117-128.
The final published version is available from De Gruyter.
The article was developed from work originally disseminated as an invited conference paper, and two refereed conference papers: one from 2009, and the other from 2008.