Plotting duration of tasks in hours, against the total number of HITs that took that that many hours to be completed. What was the resulting distribution? The usual suspect! A power law! Here is the plot:
(Since most readers do not supports IFRAMEs, those of you reading the post using a reader will need to visit the blog post to see the scatterplot.)
Interestingly enough, I observed the same behavior for individual HITs as well: while many of them are being completed in a short period of time, some of them tend to take a very significant period of time. Not sure what exactly causes the long tails in this process but seems to be something worth investigating.