San Francisco has the craziest cab drivers, but they were all very friendly.
Most were quiet until you started chatting them up.
I dropped my wallet in one cab, after paying. Lesson learned was always get a reciept, and always pay attention to the cab company.
After canceling all my credit and bank cards, our only money, I was worried about how I'd get to fly home without ID. My better half Google image searched San Francisco cab companies, and narrowed down 3 companies with similar colors. Called all three, and within an hour, my wallet was back in my hands. Tipped that driver with one of the $100 bills that was still in my wallet!
I've been to quite a few big cities, and never had a rude cabby. They are always willing to chat when you initiate it. I think they let the customer lead, and most people don't want to chat, so they don't initiate conversation. I think most frequent cab users see it as a means to an end, a service, and behave as such.