In a college town, students choose between two providers of wireless internet access. All student housing is wired for both companies, and the internet service offered by both providers is equally fast and reliable. Dozens of clothing manufacturers produce plain black undershirts. Consumers view plain black undershirts as identical and have no preference which company makes their undershirts. In a large city, one chain of coffee shops controls a large market share because locals believe its coffee tastes better than that of its competitors.