Last year, my lab at Georgia Tech created Jill Watson, an A.I.-powered virtual teaching assistant designed to help answer students' questions in the discussion forum of an online class on artificial intelligence. To assess Jill's performance properly, we chose not to reveal her identity until the conclusion of the class. Mr. Etzioni characterized our experiment as an effort to "fool" students. The point of the experiment was to determine whether an A.I. agent could be indistinguishable from human teaching assistants on a limited task in a constrained environment. When we did tell the students about Jill, their response was uniformly positive.