So, where are my robot servants?

Four years ago, researchers at the University of California, Berkeley, uploaded a video to YouTube. It featured a demonstration they'd done using a powerful new robot called PR2, a dishwasher-size machine with two hefty arms and six camera eyes on its face. In the demo, PR2 stands before a disorderly pile of small towels. Then, slowly but surely, it stretches its arms, picks up a towel, and neatly folds it, even patting it gently to smooth out the wrinkles. The robot repeats the routine until no more towels are left in the heap.