When you deposit money at a bank, you expect the bank to give it back to you. There are two things you might worry about, two sets of risks that might prevent the bank from giving you back your money. One, which we talk about a lot around here, and which is pretty central to the history and theory of banking and bank regulation, is that the bank might lose the money. Banks do not generally just keep your money in the vault. They use it to make loans, so there is risk: The loans might default, or...