If there was an economic crisis on the order of the great depression, or if, for whatever reason, the us government fell, would the internet still exist in its current state? It seems like too much of it is supported by companies that could easily go out of business and then take with it much of the internet infrastructure they support. Is this a likely scenario?
I think the form would likely change. The network links would still exist.... over time SOMEONE would take them over as long as they have access to the needed router hardware. However, certain core services (DNS) have roots that are centrally located, Do in the right set of (non-government at this point) people, and those could need to be reestablished. Most such things have steps in place to make this very unlikely... but in a mad-max style scenario I suspect we'd lose the net for at least awhile, then have a bunch of smaller nets crop up and a new 'internet' reform over time.