I've heard people refer to "Moscow face" (though oddly, not "New York face"), where people's expressions are blandly neutral, tending towards negative - it's a way of adjusting to living in a large urban center.
I'm not sure what my default face while I'm out in public is, but I've definitely got a certain expression I've learned to put on when I'm walking by people trying to sell me something, beg me for something, recruit me for something. I've had people start walking towards me, and then instantly back away when I slip that particular mask on.
It's pretty great, but I'd wager that it's an adaptation that someone living in Farmersville, TX doesn't need to use very often.