Fon, one of this year's Next Net 25, has struck a deal with Time Warner Cable to offer its free WiFi routers to its customers. If you have a Fon router, you can tap into any other Fon router that you encounter while on the road.
Why would a cable company encourage WiFi sharing? Because it effectively broadens the broadband access of its paying customers when they are away from home, which could be a selling point. You are not just buying home broadband access, but one day you might get access wherever you go. (375,000 Fon routers have been distributed worldwide, 60,000 in the U.S. alone). Add a WiFi phone to this equation, and you can see why cable companies might be intrigued. All of a sudden, given a big enough network, that gives them the ability to compete with cell phone operators.
(Disclosure: I am employed by Time Warner, which owns a majority stake in Time Warner Cable).
(Read my previous post about Fon's competitor Whisher here).