When a small neighborhood bookstore in San Francisco announced it was closing, neighbors banded together, pledging to buy a book a month and raising money to keep the store open. “This is probably not the sort of investment your accountant would suggest as a sure thing or, for that matter, even a longshot. Even if the store gets back on its feet, the investors won’t make money. Instead of interest, they get a 25 percent discount on all books they buy there. The loans will be repaid over six years.”