Wireless meshes don't work. They need to be fractal - local omnis, then cantennas, then backbones. If every geek had a cantenna (plus an omni to connect to the non-geeks, and another geek with a cantenna), you could light up most cities (OK, maybe not quite a city ... I don't really know). From there, you need some super-geeks finding ways to connect the city nets (private fiber?), but you don't need many super-geeks.