Defending a class action lawsuit poses great risk and uncertainty for a corporate defendant. A single plaintiff, whose claims may be worth only a pittance standing alone, can represent the claims of every corporate customer over a period of several years. If the court refuses to certify the class, the case properly may belong in small claims court. But an order certifying a class may transform that single claim into bet-the-company litigation. Unfortunately, it often takes months—and sometimes years—before the defendant learns the answer to a very fundamental question: Exactly how many claims are at issue in this lawsuit?