An article in Wired by Negroponte discusses wireless internetworking---the concept of having wireless hubs that are smart enough to route and talk to each other.  That way, my wireless network talks to my neighbors, which talks to a neighbor further away, and so on until the wireless system drains to the larger Internet.  I've seen this work.  A Utah company, called United Internetworking (founded by Jay Carlson) has built working hardware and software that does this exact thing in the 5GHz band.  Its actually very cool to see.

The article goes on to say:

Reallocating spectrum won't happen overnight. It is just as hard to shake up occupied electromagnetic zones as it is to bulldoze part of a city for a park or a civic center. New attitudes will have a more immediate effect as we look to higher and higher parts of the spectrum, and use them for shorter and shorter distances.

It will be harder than bulldozing part of a city.  Usually we pick on the disenfranchised when we bulldoze the city.  Spectrum is controlled by the ultra-enfranchised and they don't give it up without a fight.