I had a fascinating conversation with Bill Woodcock, who just got back from Tonga. Apparently in the developing world, 802.11 is taking over from GSM, as the access points are orders of magnitude cheaper.
Consequently, there are cellphones that run 802.11 and VoIP, but the customers don't know this, as the phones just work.
Routing round incumbent telcos this way is easier there - nations like Niu� and Tonga have open public wireless networks, and countries like Nigeria are growing urban-area wireless networks too, with huge zones bridging between basestations across town.
I was thinking the other day that for what I spend a month on cellphone services, I could buy a wireless basestation every month and put one every place I go.