The problem with wifi is that things will go downhill quickly once you have too many stations online. Even if they're not actively browsing, the normal amount of chatter that a network has will often just slow things right down. It would need to be split into smaller wifi networks linked somehow and that means someone needs to be in a central location that is easily traced.

In theory I guess someone with a very fast connection could run a layer 2 VPN. Then you could all run a routing protocol over that network which is accessed over the internet.

Lot's of ways to do it really. Wifi alone is probably the worst though.