Motivations for defensive space
See below, three very relevant occurrences of how space is transformed in the 21st century. These are 3 examples of "defensive space" (aka "defensible space": architectural and environmental design used to reduce criminality by increasing field of observation and ownership) can be found next to where I live in Geneva.
The first and the second one consist in covering the ground with concrete instead of the vague lawn that was used by drug dealers to hide their stuff. Note that the first move was (before putting concrete on that poor little tree) to break a mirror there so that drug deals would cut their hands when trying to get their heroine.
The third one is maybe less conspicuous: two pieces of steel has been put on the ground to prevent people to park their car (which nicely complements the yellow signage).
Why do I blog this? well although this is, sort of, environmental scannning 2 meters from home, it's definitely an important collection of signals that attest spatial changes. What does that mean for urban computing? I guess the next step when you're done with concrete, steel and broken mirror is to use electrons to prevent people from doing certain things.
Please see also the classical and sad anti-skateboard devices.