Cogent analysis of why WiMax/802.16 may change the economics of hot spots: It's all about the backhaul. Hot spots are fine, but you're still paying for that wired tether, and that can be a huge hunk of the cost of deployment. This column makes the excellent case that the 802.16 set of standards for long-distance point-to-point wireless has avoided weaknesses of 802.11a while including licensed spectrum as an option, making it a natural choice for hot spot backhaul.
Several companies have been working specifically on backhaul as an aspect of their system. Tropos has a mesh system that interconnects hot spot devices, but allows backhaul to be plugged in only at desired locations. RoamAD uses a variety of wireless backhaul to avoid needed wired connections throughout its ubiquitous system design.
Any time you can avoid the wire, you have the potential to drop recurring costs paid to incumbent telcos and to dramatically increase bandwidth without increasing the cost.