Herreid and colleagues have asked themselves the question raised in the title. To answer, they surveyed the more than 1,300 teachers on the Center's listserv (mostly biologists and faculty who teach health-related subjects), asking them to identify their favorite case and say what made it their favorite. “We thought it would be instructive to identify the faculty's special favorites on our website, but more important, to help us identify those characteristics that make a case good.” (p. 70)