Over the past couple of years, there's been an increase in reports coming from current and former Amazon employees who describe the experience of working at Amazon to be a complete physical and mental grind.
This video above is from a BBC series called Amazon: The Truth Behind The Click where the BBC tracked an Amazon employee at one of their UK warehouses and got a first-hand account of what it's like to be at such an incredibly soul-crushing job. Employees face countdown timers (they are given a set amount of time to walk to and find items or face penalties) and warehouses that contain row after row of items that they must walk to, sometimes racking up to 10+ miles a day while pushing heavy objects in a cart.
I suspect that Amazon is trying to reduce these damning reports by using more and more Kiva robots at their warehouses with each new year. After all, robots don't complain, they don't sleep, and they don't normally screw up -- all things that seem like they must be weeded out if Amazon intends to continue the upward tick in online orders.