Summers imagined a machine called the "Doer" that could make anything or provide any service. Productivity would soar. Wonderful goods and services would emerge. Enormous wealth would go "to those who could design better Doers, to those who could think of better things for Doers to do." But everyone else would be worthless in the labor market.Summers said the world is moving in that direction and has completed only 15 percent of the journey, but already we are "observing its consequences." Consequences, indeed. ATMs dislodged bank tellers. Microsoft Outlook manages what secretaries used to do. Expedia is replacing travel agents. E-ZPass is doing away with toll-booth operators. And robots continue to supplant factory workers. But surely some jobs are safe. Truck drivers, perhaps? A machine can't negotiate a left-hand turn against oncoming traffic without a human behind the wheel, can it? Or so economists Frank Levy of MIT and Richard Murnane of Harvard University reasoned in their book "The New Division of Labor," way back in 2004. That was then. Six years later, Google developed a car that could drive itself, crossing the Golden Gate Bridge, circling Lake Tahoe and cruising down Hollywood Boulevard. The gee-whiz driverless car could soon claim victims in the job market. "Twice a week, a truck comes near my house, and two guys get out and pick up the garbage," says Vardi, the Rice computer scientist. "This will disappear. There will still be a truck coming, but it will be driven autonomously, and the garbage will be picked up autonomously, and those jobs will be gone." In the United States alone, 92,000 people are employed as sanitation workers, according to the Bureau of Labor Statistics. Add all other driving occupations, from long-haul truckers to taxi cab drivers, and the total exceeds 4 million. All those jobs may be in danger.