In a world driven by hard cash, idealism always loses in the end. The problem was Quora's revenue model - incentives always, without exception, determine outcomes. But of course without a snazzy-sounding revenue model, Quora wouldn't have been able to raise so much VC money, and so it doomed itself from that point onward. Wikipedia understood this trap; hence it never adopted a Quora-like way to pay the bills.