... The market demand for information, like the market demand for protective bumpers, will not fully reflect its social benefits. Because of external benefits, the quantity of information produced ... benefits, from safety caps for drugs to protective devices for explosives. This argument does not justify unlimited government intervention, however. We cannot conclude, for example, that all automobiles ... rule applied to contracts: the buyer was responsible for what he signed. Although consumers could sue sellers for breach of contract or for fraud, no government agency would initiate the suit....