Humans continue to have another advantage over robots: They remain a more flexible workforce. To handle this year’s holiday shopping season, Amazon.com (AMZA) hired 50,000 part-time workers. While seasonal, part-time labor is not something you can necessarily build an economy on, it’s worth noting that Amazon didn’t buy more robots, because you can’t hire a robot part-time (yet ). What would additional robots do when demand receded? “Come January.” Says Jim Tompkins, a supply-chain consultant, “all that automation’s going to be staring you in the face.”