Classifiers have been quite successful in a variety of domains ranging from the identification of fraud and credit risks in financial transactions to medical diagnosis to intrusion detection. Basu et al. (1998) built a hybrid recommender system that mixes collaborative and content filtering using an induction-learning classifier. Good et al. (1999) implemented induction-learned featurevector classification of movies and compared the classification with nearest-neighbor recommendation; this study found that the classifiers did not perform as well as nearest neighbor, but that combining the two added value over nearest-neighbor alone.