Very good points. Actually, a user's net owned by subscribers already was very successful on the island of Alameda in California. Users were not impacted much by the sorting going on in the background that turned their tower computers halfway into servers. The cost of buying bulk internet is very low, and with no ISP, they paid almost nothing for the service and the broadband speed was tremendous since it had multiple connections to the web and would split up pages among them.
They got bought out for millions a few years ago, so it's now gone, I think.
But from a technical standpoint, it's easy to do. Your computer already posses everything necessary to wi-fi hop all over your community by line-of-sight. It's the political reality of living in a police state that outlaws everything that is the problem. Here in the Philippines, the government is working with google's intent to make broadband available free for all. We'll see how it turns out.
Here's one in Oakland I just stumbled upon: