Address clustering intuition

This has probably been thought of before, or discussed on some other list, and if so I apologize in advance. I've formed an intuition that, if all IP addresses were portable (ie. independent of ISP) and assigned on a strictly geographic basis, then there would *automatically* be clustering of addresses equivalent to that obtained from CIDRization as a result of marketplace forces and the practicalities of technology. Note that this results from the address being, not the property of the ISP or the end user, but rather of a geographic location. In other words under my scheme if I picked up and moved a hundred miles I'd have to renumber, but if I just switched ISPs I wouldn't. -- Walt