That's an expensive proposition, but not nearly as pricey as offering cable-based high-speed Internet access. It costs between $20,000 and $50,000 per square mile to build a Wi-Fi cloud. That's four times less expensive than the cost of burying high-speed data cables under city streets. Cities aren't worried about excessive upkeep costs, because they say the networks are low-tech, low-maintenance operations.

They may have a point. Wi-Fi clouds consist of thousands of Wi-Fi antennas, or "nodes." Each node is basically the same kind of Wi-Fi router that, say, a coffee shop might use. With a Wi-Fi cloud, a couple dozen of those routers are placed at regular intervals over a square mile, and they all communicate with each other and with a single, wired Internet connection. The mesh works much like the Internet itself. Data flows from node to node, depending on which one will give you the strongest signal. A failure in any single node won't bring the network down, because the other nodes will fill its place. Every mile or so, another wired connection is plugged in, and another set of nodes is put up - most of which are attached to lightpoles that also provide power. The result is a chain mail of connectivity that's accessible anywhere outdoors, and can be brought inside with the purchase of a separate wireless antenna.

"It's a completely towerless system," says Joe Hamilla, director of engineering for Motorola's Mesh Networks Product Group. "So instead of having to buy real estate, go through planning boards, and get approvals,­ these things hang on existing lightpoles and buildings. No one says they don't want this in their backyard, because they don't even see it."