My experience is that if you do not look like a white yuppie, cabs won't even stop for you to refuse service, especially at night. I once grew a goatee that made me look Hispanic, and I couldn't hail a cab at night to save my life.

I was upset about this and even once filed a complaint with the Taxi and Limousine Commission (TLC) after a cab slowed down, looked at me, then sped away to pick up a white guy down the street. However, for the complaint to result in a sanction, you have to show up at the TLC court to testify, or the complaint is tossed. I didn't want to spend a day in TLC court so I didn't follow up.

When it got warmer, I shaved my goatee and stopped wearing my leather jacket. Magically, I then got picked up every time. I was disgusted by this and now I take cabs only in extremis.