> The deep learning is that there are forces that lead to centralization: generally they are variations of human choice and seeking economies of scale.

The reason that some airports are hubs and some are not is due to the the fact that it's a system spanning large areas of varying densities. Distance doesn't exist much on the internet, other than firewalls. The goal of most internet companies is to create that distance through lack of interop, in order to guide the maximum amount of traffic through a single point where it can charge a toll. It's typical rent-seeking. I'd argue that a bureaucratic metaphor is far more apt than any spatial one.