On Melbenan Drive just west of Atlanta, sunlight falls onto a long row of well-kept lawns. Two dozen homes line the street; behind them wooden decks and living-room windows open onto vast woodland properties. Residents returning from their jobs steer SUVs into long driveways and emerge from their automobiles. They walk to the front doors of their houses past sculptured bushes and flowers in bloom. For most people, this cozy image of suburbia...