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Digg, which in its heyday was effectively run by its power users, is dying. Wikitravel is probably joining it: two-thirds of its admins want to jump ship to the greener grass of the Wikimedia Foundation. Who in turn have their own people problems–a stubborn gender gap and a diminishing number of active admins. Meanwhile, across the Web, people are asking “Is StackOverflow being ruined by its moderators?�

There’s a common thread here. Site starts up; site scales; a power-law minority of its users become its key community, and if/when that community withers, the entire site is endangered. The examples above are edge cases who explicitly assign admin rights to unpaid users, or take the power law to its extreme. But they indicate a larger point.