When a bunch of people in a neighborhood, either houses or apartment buildings start stringing EtherNet? together and setting up internal sites or access to the InterNet.
You get this "for free" on a cable modem network, except you're not supposed to look at your peer nodes. Except there is always someone there sniffing your packets.
Ah, but in a true CommunityNetwork?, you're not paying for InterNet access unless you want it.