you can hail any car on the street

This makes a lot of sense. New Yorkers might charge more. I would guess the biggest objection would be safety -- how do you know you're not getting in the car of a kidnapper, thief, rapist, etc.?

On one hand, I think people greatly over-estimate that risk. On the other, many criminals likely would take advantage of the service to find victims.

What do the Kazaks do about that?