Well this idea is not exactly rocket science - some years ago several start-ups mostly unsuccessfully tried their luck in building citywide coverage with Wifi networks. Now its Metrofi trying to invest the $9 million securely from August Capital.

"MetroFi builds community area networks that deliver multi-megabit consumer wireless Internet access. Using enhanced technology based on the popular Wi-Fi (802.11) standard, MetroFi combines a new level of affordability with the convenience of portability to offer highly competitive broadband access services."