This is published under the terms of CC BY-NC-ND 2.0.
A folksonomy is ostensibly an information structure built up by the “wisdom of the crowd”, but is the “crowd” really doing the work? Tagging is in fact a sharply skewed process in which a small minority of “supertagger” users generate an overwhelming majority of the annotations. Using data from three large-scale social tagging platforms, we explore (a) how to best quantify the imbalance in tagging behavior and formally define a supertagger, (b) how supertaggers differ from other users in their tagging patterns, and (c) if effects of motivation and expertise inform our understanding of what makes a supertagger. Our results indicate that such prolific users not only tag more than their counterparts, but in quantifiably different ways. Specifically, we find that supertaggers are more likely to label content in the long tail of less popular items, that they show differences in patterns of content tagged and terms utilized, and are measurably different with respect to tagging expertise and motivation. These findings suggest we should question the extent to which folksonomies achieve crowdsourced classification via the “wisdom of the crowd”, especially for broad folksonomies like Last.fm as opposed to narrow folksonomies like Flickr.