Last week at DEMO Whisher was presented and many a comparison to FON was made.
FON offers a very inexpensive solution to the carrier as a way to authenticate onto a network without the network operator having to install new access points all over the place.
If this happens it will mark the first major carrier who has said "hello" to a 2.0, people's access approach by using WiFi to be the way to widen their reach for Voice. If it works this could also spark the growth in sales for dual mode phones like the Nokia N80i, E61 and others as well. Lastly, since BT is no longer a mobile operator, it could put a dent into the sales of the traditional mobile operators.
More on this from Glenn @ WiFi Net News.