via Bernardo Huberman:

By writers, Bernardo A. Huberman, Daniel M. Romero and Fang Wu, a paper analyzing Youtube views to demonstrate how attention and productivity work with crowdsourcing.

In the abstract:

We show through an analysis of a massive data set from YouTube that the productivity exhibited in crowdsourcing exhibits a strong positive dependence on attention, measured by the number of downloads.

You can download the paper here.