Basically, Fon is an attempt to create a high speed wireless internet network using millions of short range WiFi hubs. But having private users and high street entrepreneurs own and run the equipment from their own private board band connections! It could well work, as they are subsidising their wireless routers (by selling them at a loss now while building up the network as fast as possible) making them as cheap or cheaper than standard ones u'd use to share you broad band anyway! (so y not get one guys?!)
It's very ambitious, mostly with respect to actually having the technology work reliably (WiFi ain't all that stable when u're sat at home by your router, let alone wondering the streets!). Getting applications like Skype to seamlessly hand over between hubs would be key (i presume that's not possible yet). Idealy it would auto fall back to a 3G (descendant) mobile service when out of Fon coverage. But Prof. Mike Walker assured us that would be too technically challenging...(well that would be the line of a mobile carrier with regards to a technology specifically designed to ease the transition way from their services!)
In theory it could kick mobile phone operators up the arse, hopefully spurring them to bring out better/cheaper mobile data services asap in preemptive competition. Ideally, one of the operators would/will realise the massive benefits of this technology movement and team up with Fon, forming a robust hybrid mobile data network. It would trash the cometition in cities and build up locations once the handsets/software becomes reliable enough to cope with the more complex system.
(Above: orange dots and green smudges are hub locations in Reading. Given that i've only just heard of Fon, that's not bad! But there will need to be a few doublings in popularity.)
The Fon network would be ideal for street level navigation applications, especially in cities where GPS type signals maybe particularly unreliable. U wouldn't need more than the faintest of WiFi signals to identify a hub, look it up in a POI (points of interest) type list and start narrowing down your position. It would be far easier to install WiFi hubs in underground locations (tube stations and maybe even road tunnels when handover techniques step up a level or 2. I forgot to check if the London Underground has any type of mobile phone service the other week) and on planes/ships/inside major buildings.... A Fon mobile carrier partnership would have good incentive to install infrastructure in busy public transport locations as it would give another edge over pure mobile Operations. I recon they'd have to start following suit with they're own WiFi/WiMax hardware if they couldn't get a similar deal with Fon (or an equally ubiquitous entity). Cool