[gobdovan]

Yeah, that's part of it. But I'd argue that once you look at a city, you look at constructions administratively designed by men, with their preference for hierarchies. Try to hierarchically describe to someone instructions to pick a random leaf in a dense tree (ironically, we use them as a metaphor for hierarchical organisation) and see how far you could go in the same way you could point them out to pick a paper in the city.

Not in a position to argue about physics, but I could think of quite a few things that are better described as web-like phenomena rather than hierarchical ones, electricity in a complex circuit comes to mind.