The same problem exists in Ingress as well if you live in even a moderately populated area. Ninantic's core issue (in my mind) is that the longer their games run, the less approachable they become. They haven't figured out a solution for Ingress, so I'm skeptical that they'll figure out one for Pokemon Go.

Granted, Ingress is a little more "hardcore" in the sense that it's not really focused at a more casual market like the Pokemon franchise generally is.