> That seems to be one of the fundamental paradoxes in the anarchistic ideal of Bitcoin - that implicitly, collective action to centralize and exploit the system is a perfectly legitimate act within its framework, if you can get away with it.

I'd say it's more a libertarian ideal. You'd have the same idea in an actual anarchy of course, except that rolling up all the communes by force wouldn't be considered legitimate just because you're able to do it.