Living in the wrong cities. I live in (near) a middle-sized to small city. I can talk to nearly anyone on the street or in a shop, and I often do. I can make faces at strangers' babies and get them to smile, and get a smile back from the parent. I imagine if I cried "Is there a doctor here who can help?" while standing over an injured person, two or three people in the immediate vicinity would instantly respond (if they weren't already hurrying to the scene).

Yes big cities can be alienating. That's why I opted out.