[W]hat makes this work so darn good is that it so perfectly embodies the four ingredients required to create good candid street imagery; an imaginative eye, the ping-pong timing reflexes to react to that imagination, the technical skill to actually use a camera to get the shot, and, most importantly, the courage to actually do it.
I'm not familiar with Stochl's work, but I think Tanaka has a good summary of good street photography.
I've long been intrigued by street photography. At times, I think I'd like to try it seriously. However, one of the things that worries me is the issue of privacy.
Normally, when you publish a photograph of someone, when they're not just a small detail in the picture but the main topic, you need to get their approval, even if they were in a public place when the photo was taken.
This is entirely impractical with street photography. You can't go around taking pictures and then running after people to get them to sign model releases.
I've no idea how professionals deal with this.