Jennifer Buetter, a Maryland housewife, has gone into the placebo business, selling sugar pills that parents can give to their children in lieu of medicine. Doctors have long noted that patients who believe they are taking medicine, even though they are only taking sugar pills, often show improvements, especially for minor complaints. The illness is largely in their heads. Ms. Buettner believes parents can soothe their cranky children the same way. Some doctors, however, disagree. And in any event, placebos should not be used in cases where real medicine is called for.