Data mining challenge problems: any lessons learned?

When considering the merit of data mining challenges, we need to answer the question of whether the amount of academic outcome justifies the related expense of scarce research time. In this paper I will provide anecdotal evidence for what I have learned personally from participating a various challenges. Building on that I will suggest a format for challenges that tries to increase the amount and improve the quality of the academic output of such challenges for the mahine learning research community