If I encounter anyone while walking between my house and the metro station, or otherwise around the shops and stuff in the neighborhood, people tend to look me in the eye, smile, say hello, etc.--regardless of whether we have been introduced or not. Once I get on the metro and head downtown, people stop doing that so much, although I think people around here just tend to look at each other more than I am used to. I've noticed other people on the metro or the bus idly looking at the other passengers.
I guess I always assume people are looking at me because I am quite, ahem, plus-size. Maybe I dress funny, too, and don't realize it?