[21] See, e.g., Don Peppers & Martha Rogers, The One to One Fieldbook (1999) (discussing the value of firing a company's least profitable customers, called "below zero customers"); Gary McWilliams, "Minding the Store: Analyzing Customers, Best Buy Decides Not All Are Welcome," Wall Street Journal, Nov. 8, 2004, at A1 (describing an initiative by the Best Buy retail chain to get rid of unprofitable customers).