John Naughton's online diary contains a good piece on Wikipedia.
Me: “So you’ve found a glaring error on a subject you know about?”
Critic: “Yes. Elementary mistake”.
Me: “So why haven’t you corrected it?”
Critic: Flustered (sometimes), irritated (often), defensive (much too busy)
But there's another aspect to this, which is the wiki-zealots, who are all-too-ready to block the Critic who does have expertise on a topic precisely because they are not members of the Wikitribe.
Eventually, those people give up and keep their expertise to themselves, doing Wikipedia and the world a disservice.. Well, Wikipedia is doing itself a disservice, but let's not quibble.