There's a growing appreciation among executives that the returns from big data are real indeed. But that doesn't make moving forward any easier. The investment, both in dollars and management commitment, can be large. CIOs stress the need to entirely remake data architecture and applications. Outside vendors hawk the power of black-box models to crunch through unstructured data in search of cause and effect relationships. Business managers scratch their heads — while insisting on knowing upfront what the pay-off will be from the spending and the potentially disruptive organizational change.