2) To those suggesting you get in the cab before you state your destination, the cabs that do this already know that it is harder to refuse you once you get in the cab. That is why they will leave the doors locked, roll down their window, and only partially position themselves in the stopping lane.... They are ready to veer off very quickly. When it is raining outside and you are desperately trying to catch a cab you are going to comply with this routine.
3) Also, if you do manage to enter the cab and tell them a destination that is out of the way of their return journey, they have no qualms in telling you to get out.
EDIT: I'd also like to add that Uber hasn't really brought anything new to New York other than a smartphone app. Town car services in New York City are more than plentiful and no less reliable when you call them up than when you request one through Uber. In my my experience, the town car companies I have used over the past decade have been much more reliable and quicker to service me than the few times I've tested out Uber's service. I wouldn't call Uber a disruptive service in the NYC ecosystem, just a complementary channel for requesting private town cars.
It does make me think though, why should these town car services even cut Uber into the loop? Maybe there is space for some type of PAAS for town car companies to roll out their own web and mobile based booking system?