Our recent set of posts on the topic of illegitimate predictors was provoked by a fascinating recent paper on the topic presented at the KDD2011 technical data mining conference. The paper, by Kaufman, Rosset, and Perlich, focused on public modeling competitions. Such competitions have been in vogue since at least 1997 when the first KDDCup was conducted, and were given a terrific boost when Netflix offered a $1 million prize for a movie recommendation system that could beat their own internally–developed system.