Carol Tenopir et al. have published "No Scholar Is an Island: The Impact of Sharing in the Work Life of Scholars" in .
Here's an excerpt:
In an international survey of 1,000 published scholars, the Beyond Downloads project examined their sharing behaviours in order to gain a more contextualized and accurate picture of their usage beyond download patterns and citation counts. Scholars share published articles with others as a mode of content discovery and dissemination, particularly if they work in groups, and most expect to increase their sharing in the future.