> "Unlike real serfs Uber drivers can set themselves free at anytime (i.e. quit)."

I'm certainly not on the Uber-hating bandwagon that's been doing laps around HN lately, but this isn't always true. Some people drive an Uber car because they need a paycheck and a flexible schedule, not because they want to. There may not be many (or any) other opportunities ready available.

A serf could quit too, as long as he was willing to abandon everything he knew and set out on the road going far away from his old master. But he knew he'd probably end up destitute and serving a new master in a strange place, so he stayed.

People are risk averse. Some people do jobs that pay bills because they need them, not because they want them. Freedom to walk away from something doesn't imply a desire for that something.