Its not untrue though, is it? Its really easy for such communities to really rapidly degrade.
That SO and wikipedia have both retained quality for so long, while also having strict moderators hunting a strong ideal, in areas where so many of their peers have fallen prey to the unwashed hordes, implies that it may not be so easy to discard the strategy.
It might even be necessary at such large volumes. The particulars of their activity might be maleable, but just approaching the problem (very) defensively might bot be.