People in New York seem to talk to one another more than Londoners.
I've been spoken to on the subway, in cafes, in lifts and in the street much more than any other place I've ever been. They're either asking for directions (which I'm proud to say I can usually help with to some degree), they're mad, or they're drunk.
Bars are great places to strike up conversations. New York's booze scene is normally arranged with stools set at the bar just asking to be sat upon. That way you get to converse with the barperson and your neighbour.
Once, someone walked with me the entire length of the Brooklyn Bridge telling me the history of its construction and other strange stories from its history, only to vanish at the other side with nary a word.
All quite unexpected for an introverted Englishman.