[JoshTriplett]

> One potential issue that comes to mind is that people might be more frivolous with a rating than with real money.

When you rate someone lower than 5 stars, Uber prompts for an explanation. And if you provide one, it often generates a direct followup from Uber support trying to address the problem; if there was anything seriously wrong, addressing the problem often includes either a full refund or some small credit for future rides, and some indication that there'd be an attempt to solve the problem. I think that's a pretty reasonable way to keep ratings meaningful, and actually address any problems that produced a low rating.

So, I actually feel like there's more connection between a rating and actual action, whereas choosing whether to submit a tip or not seems very likely to correlate with factors other than the quality of service.