Only problem with Wifi is the limited reach it has. You would literally need every other neighbor to be setup the same for it to work.
That's why you use mesh networking. Everybody participates in the mesh and provides a path to other nodes. I used an OLSR network to allow the locomotive on a long train to pass messages both ways down a long train...even if it was wrapped around a mountain. A line of sight 802.11b can pull off a 1 mile link with off the shelf hardware. I've used custom hardware with bigger power amps on a large airplane to achieve links over 50 miles.