The Economist has this on spatial "clustering."
Agglomeration economies and growth economics are slowly coming together in the literature -- as they must in a non-agricultural economy.
Chris Webster and Lawrence Lai have written about the "spatial order" -- as one of five spontaneous orders. This makes great sense as we are describing the continuous evolution of supremely complex and organic systems.
These systems resist central planning, which is moderately ironic because "smart growth" is all the rage. But one only has to take a close look at the similarities of urban forms in the developed nations (Europe and the U.S. in this cite), to see that policies are trumped by preferences. Here is a case where international comparisons are the place to start.