> If this ever happens to you, the answer is simple: tell them, "thanks for the free ride".
Done that on rides from JFK. Been threatened for a while. Like physically. Then suddenly the machine worked. Oh wonder.
The first time this happened to me, also JFK, I was half delirious after an intercontinental trip with long delays. The first time in the US. So back then I didn't feel like having a forceful confrontation with a cabbie I had a hard time understanding.
I think that's much less likely to happen to you if you live there. But it's usually pretty easy for a driver to recognize whether you're from NYC. Language, destination, asking outright...
EDIT: typo.