When I was doing my barefoot project everyone asked me if I was worried about broken glass on the ground. Well, either that or they asked me how often I had cut my feet on broken glass on the ground but either way the answer was about the same...
To be sure, I *saw* glass on the ground here and there and sometimes there were bits of glass in the crevices of the pavement but it was never an issue. Today I stepped directly on a piece of broken, jagged glass with bare feet for the first time. I felt a pinch under my foot, shifted my stance, continued to feel a pinch and then lifted up my foot to find a shard of glass stuck to it. I peeled it off and noted that absolutely no damage had been done even though 3 distinct pointed edges had been trying their best to pierce my flesh.
So there you go. It turns out I am largely invulnerable to glass. In even more ironic news the glass was not located on a sidewalk, nor even a park but rather in the elevator in my building. So much for the outside world being dangerous. :)