"New “mesh” wireless networking gear—which lets people share Internet access something like BitTorrent lets them share files—has made it easy and inexpensive to create decentralized networks. Wireless mesh networks are now being used in locations as diverse as low-income housing projects, Indian reservations and South African schools. Citywide (or nearly citywide) mesh networks are being built in places like San Francisco and Urbana, Ill. Internet access becomes much less expensive because neighbors can share a commercial DSL connection in the same way that co-workers in an office do.
However, mesh networks tend to be less decentralized in practice than they are in theory, and for technical reasons any really large mesh network seems to require a degree of structure and management. And even a decentralized mesh network is dependent on an ISP to communicate with others outside the neighborhood." (http://www.truthdig.com/report/page3/20081024_e_speech_the_uncertain_future_of_free_expression/)