They are pretty big in japan. I've noticed a big increase in the past year or so; a lot of places that previously offered their own free service now have a for-pay Fon access point. (in the Kobe area, anyway)
In Portugal, Fon partnered with Zon (an ISP operation of the major cable TV provider). A couple of years ago, the cable-modem/wireless-router combo boxes, mostly Netgear hardware, had an option to turn on the Fon service, which was off by default.
That must have been not working very well. So, around August 2010, they updated the firmware in the routers, including those already deployed, to turn on the Fon option by default. Plenty of access points now available ...
(Details: although it uses the same radio and bandwidth, the public Fon access point uses a different IP; it requires a password which anyone who provides Fon access in his wireless router can have by registering with fon.com)