  The tragedy of the digital commons does not prevent the copious voluntary
production of content that one witnesses in the web. We show through an
analysis of a massive data set from \texttt{YouTube} that the productivity
exhibited in crowdsourcing exhibits a strong positive dependence on attention,
measured by the number of downloads. Conversely, a lack of attention leads to a
decrease in the number of videos uploaded and the consequent drop in
productivity, which in many cases asymptotes to no uploads whatsoever.
Moreover, uploaders compare themselves to others when having low productivity
and to themselves when exceeding a threshold.
