If you had an antenna and an omni, though, you could connect a local subnet to the wider area. If you had a few directional antennas in each local subnet (say, an apartment complex connected by omnis), then the subnets would connect to the rest of the world.
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.
