Ponzi schemes come in many sizes. The colossal fraud engineered by Bernard Madoff is an occasion to rethink the legal rules and remedies associated with such episodes. But then there are smaller Ponzi-like schemes, such as fraud in law school admissions, and the question of whether law does or should play any role. At the other extreme are nation-size Ponzi schemes, such as our recent mortgage-and-foreclosure crisis and, similarly perhaps, long-range deficit spending in many countries, such that one generation defrauds another. In this CBI, Professor Saul Levmore asks why law might be much better at one of these levels than at the others. Concrete problems can help us understand law's comfort zone, or its proper domain.