Via avocadia, the efficiencies of social organisation: "From 1100 onwards, Europe enjoyed an efficient urban system with positive feedbacks between cities (based much more on sea and river trade) in spite of the fact that it remained politically fragmented. In the Arab world, by contrast, the neighbourhood effects disappeared. There the break up of the Abbasid Caliphate was eventually followed by a new empire, the Ottoman Empire. To some extent, this took over the role of its predecessor - but without restoring the efficient system for economic exchange that was present during the Golden Age of Islam."
I was recently at a resort in Mexico. There was a curious relationship between the merchants on the beach and the resorts themselves. The resorts had private security and were rigourous in enforcing that only people staying at the resort could be in the common areas. However the beach was public land, yet the merchants stayed a respectful twenty yards from the resort edge.
I am not sure if it was because of the resorts enforcing some boundary, or owning some of the beach, but there was a definite artificial boundary. The merchants were respectful when given a "no thanks" as well. Not bothering the tourists once no interest was shown. (more)
I am not sure if it was because of the resorts enforcing some boundary, or owning some of the beach, but there was a definite artificial boundary. The merchants were respectful when given a "no thanks" as well. Not bothering the tourists once no interest was shown. (more) 
