NPR reports in some depth on Phila. Wi-Fi in a 4 1/2 minute report: One Philadelphia city council member wonders if, with all the failures to build Wi-Fi networks in cities across the country, whether that means there's no market for it. I'd argue that the technology and cost underestimations coupled with overoptimistic business plans, and a lack of real partnerships between cities and the entities building the networks have more to do with the prominent failure.
Sascha Meinrath of the New America Foundation states the municipally owned networks are moving ahead, while corporate networks are failing. I think that's the wrong characterization, but Meinrath and the group he's affiliated with have a specific ideology that puts everything in those terms. This doesn't explain Minneapolis's network, which is apparently working well and ramping up to a cash-flow positive state. It's really more about cities putting up money into networks, whether their own or ones being built for them. (You can read my long critique of the foundation's report on Philadelphia Wi-Fi.)
In networks where cities have a financial commitment to build the network or to buy services, these networks are generally being built. The economics of large-city Wi-Fi was distorted by EarthLink's upfront willingness, then echoed by other providers, to build networks at no cost to cities with no commitment to purchase services.
The punchline for the story is that while the network is still being built in Philadelphia, very slowly, everyone's waiting for the shoe to drop.