Then don't tell the driver until after the ride starts. Maybe also require that the rider is near the driver before that happens or that the rider presses a button to send over the destination.

Indeed; I further presume that if it was implemented, drivers would move to only accept fares that provided a destination location.

Some of my friends work in bars and want cabs to get them to their less than ideal neighborhoods at 3am or later. It's already very difficult for them to get a cab to take them to a questionable neighborhood once they're in the cab; having to front-load that information could make this much worse.

(Many municipalities require cab drivers to not discriminate. Obviously they do anyway, but I presume that Uber drivers that aren't medallion / license holders have even less impetus to go into these neighborhoods at odd hours.)

Regarding the last point: true, drivers would have to be required to dash-mount their smartphones in a similarly fashion. This setup would certainly be much safer than the current one, where they’re paying attention to a mounted GPS and their non-mounted smartphone running the Uber app.

Also – maybe at some point in the future, the Uber driver’s app can run directly on the car’s on-board computer system – now that would be nice, wouldn’t it?

I don't see what is inherently bad about that. If there is a route drivers don't want to take, shouldn't the free market push the price higher until they see it as worth it? (While per-route pricing differences might add complexity, that's exactly the sort of complexity a software company should be able to handle.)

If Uber's goal is to get regulated out of existence as fast as they possibly can, a great first step would be to allow drivers to screen fares by destination.