In addition to that, most of those megaminers, and megapools, can't do much without working with a large chunk of other miners. Without it, the worse they can do is not fulfill individual transactions (which other miners can continue to accept).
Just because a minority is hoarding bitcoin, does not make bitcoin's core issue invalid, that is, don't trust financial institutions or governments.
Bitcoin never claimed to solve the issues that are at the core of monetary systems (greed, corruption etc). It solves the issue of trust. I don't have to trust a financial institutions or government to tell me how much money I own. Nor is there a government or bank that can freeze my account because I've been naughty (or, in certain cases, because the government deems you naughty because of $ideology). That's what bitcoin solves. Not the issues that are core to monetary systems. Issues that mostly come from human psyche.
