...unless they only wanted to talk to each other. But you can get a decent connection and spread the cost among a few dozen people.

I'd caution that meshes can be a little on the slow side - so depending on the number of people, what they want to do and and how spread out they are, you might do better with a bridged solution.

that mesh networks could prevent a top-down black out as happened in Egypt. But it seems, one would still need to go to one of the few large ISPs for a T1, T3?? line?

Theoretically, is it possible for separate networks to talk to each other? In other words, could these networks become so large as to connect people from different cities? I have a very rudimentary understanding of networking. My apologies if these are dumb questions.