You sound as if we're living in two different worlds. I can imagine that you've witnessed such people, committed enough to the idea of protecting people from predatory capitalism that they were willing to invest their money and efforts into something without aiming at making more money, but I've never seen such an enthusiasm.
In order to think so, one should have enough money for satisfying all his primary needs (food, shelter, clothing) and not worry about them being in place in the future. But once a person reaches this level, greed take over. Well, perhaps, in America people are more altruistic in nature, I don't know. Here, in Russia, I've never seen anything like that. Oh, I heard some talks of it, but never seen any action that was pure and didn't have any hidden goal (like tax extemptions or things like that).
Well, then again, perhaps I'm too pessimistic about humans.