People often download it into offline storage, i dont see why we couldnt just make our own.
That said, I am one of the people who downloaded a copy of Wikipedia. It wasn't with the intent of working it. Rather, it was to wait out any political strife (since that is bound to happen with such a large and diverse audience).
There's Internet In a Box and various other offline self hosted interfaces.
But of course there's a big difference between a mirror of the content and the whole community which updates and creates the content.