For the rest of us who hold the occasional door without tip or guarantee of monetary retribution, the feeling that you can wind up holding the door for every living person in New York arises every now and then. The door is held and here comes the never-ending line of people-- some of whom acknowledge the gesture and others of whom ignore it completely. Generally I find it my duty to let go of the door if no acknowledgment comes-- whether or not it swings right into the person's face.
For a while I felt rude doing this, but once I realized that these people are most likely skating by on doors held open for them all over the city and thus living the life of ridiculous privilege. If I don't let go of the door I may as well get a crimson suit with gold braiding and an impressive hat.