Maurice Lim Miller, the recent recipient of a MacArthur Foundation "genius" grant, runs a nonprofit that studies families living on a median income of about $26,000 in San Francisco and Boston. Instead of pointing the families toward social services or other programs, Miller gives them about $160 a month to document the ways they're working to get out of poverty. They could choose to pay down credit card debt or hire a tutor to improve their children's grades. But more often than not, they choose to become entrepreneurs.