There is so much in Vernon Smith's Nobel acceptance speech (recording here and reprinted recently in the AER) that I have been going back to it more than once. Start with the three quotes that he begins with. Look at the one by Herbert Simon.
We have become accustomed to the idea that a natural system like the human body or an ecosystem regulates itself. To explain the regulation, we look for feedback loops rather than a central planning and directing body. But somehow our intuitions about self-regulation do not carry over to the artiﬁcial systems of human society. (Thus) ... the ... disbelief always expressed by (my) architecture students (about) ... medieval cities as marvelously patterned systems that had mostly just “grown” in response to myriads of individual decisions. To my students a pattern implied a planner ... . The idea that a city could acquire its pattern as “naturally” as a snowﬂake was foreign to them (Herbert Alexander Simon, 1981, 1996, p. 33).
Cities as snowflakes does not mean that the cities or the snowflakes involve a central planner. I often cite an old David Brooks NY Times Magazine piece (April 9, 2000) in which he notes that, "The ritziest suburbs are filling up with urbanites who swore they'd never live there. To make them feel at home, retailers are rapidly turning suburbia into SoHo." We get this outcome (and an uncountable number like them) from markets, not planners.
A propos Brooks, my student Qian An has found that the average time spent to get to a shopping destination in the large U.S. metropolitan areas was just over 14 minutes in 2009. It was just over 13 minutes in the suburbs. The travel time variance was also smaller in the vast and "sprawling" suburbs. That is one nice snowflake.