Alyssa Katz on how housing speculators are hindering efforts at block-by-block revitalization: To get to Pittsburgh, a historically black neighborhood south of downtown Atlanta, I drive past several boarded-up and burned-out homes. Turning onto McDaniel Street, I steer around a pile of clothes and toys spilling out into the road. "Lord, behold, a family's house foreclosed and their possessions just thrown out there," says LaShawn Hoffman, CEO of the Pittsburgh Community Improvement Association, from his storefront office down the block. This is one of the vastest foreclosure zones in the nation. On maps of bank sales, Hoffman observes, "you almost can't see the community because of all the red dots." His organization has counted them: It found six out of 10 homes in Pittsburgh are now vacant, casualties of foreclosure with wood planks and metal shields guarding their windows. Hoffman's group mows rangy lawns and bolts houses shut before squatters, prostitutes, or drug dealers settle in. KEEP READING ...