Installation is quick, too. In Philadelphia, officials think they can install a square mile's worth of nodes in half a day's time. That's about how fast things went in Chaska, Minnesota, one of 29 smaller U.S. communities already covered by Wi-Fi clouds. That entire city got Wi-Fi access in just a few weeks and at a cost of less than $600,000. Service there costs residents $15.99 a month, and nearly a quarter of the population is signed up.

Then again, Chaska is not exactly a bustling metropolis. Just 18,000 people live in the city's 16 square miles. By comparison, Portland, Oregon, which may be the first to follow Philadelphia, has 538,000 residents living in 130 square miles. Philadelphia, meanwhile, has 1.5 million people in 135 square miles.

In cities that dense, there's a lot of stuff flying through the air. Cell phone calls, cordless­-phone chatter, two-way radio transmission, Donovan McNabb passes. That kind of thing. And with all that competition, no one knows if a big-city Wi-Fi cloud will work until it's built. "This kind of network has never been deployed in a city as dense as ours," says Neff, Philadelphia's CIO. "But we're confident in the technology."­

Right. Technology. Regardless of how the politics shake out in the cities pushing Wi-Fi clouds, the march of technology is likely to be unstoppable. Perhaps someday all cities will have Wi-Fi clouds. Or maybe we'll all log into WiMax networks, a successor to Wi-Fi where a single wireless connection can be sent over several miles. And with cities desperately looking to gain a competitive edge on each other, more wireless Internet access is almost certainly on its way soon to a city near you.