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Anti-elitism at Wikipedia is at the root of both of its biggest problems, and its greatest strengths.
The negative effects of anti-elitism are obvious:
lack of public perception of credibility, particularly in areas of detail
the dominance of difficult people, trolls, and their enablers
creation of an unwelcoming environment for editors with disciplinary expertise
The positive effects are perhaps less predictable, but are demonstrated in effect by the success of Wikipedia's anti-elitist model, compared to more restrictively "elitist" projects like Nupedia or Citizendium.
maintaining Wikipedia involves many "menial", repetitive tasks that expert editors would not want to bother with, but which are embraced by anti-elitist editors
intelligent non-experts can compile perfectly encyclopedic articles by referring to tertiary sources (paraphrasing other encyclopedias and introductory textbooks).
Flawed articles due to trolling or pushing of fringe scholarship may have the effect of motivating educated editors to invest effort much more than an invitation to expand a short but innocent stub article would.
The Wikipedia philosophy can be summed up thusly: "Experts are scum." For some reason people who spend 40 years learning everything they can about, say, the Peloponnesian War -- and indeed, advancing the body of human knowledge -- get all pissy when their contributions are edited away by Randy in Boise who heard somewhere that sword-wielding skeletons were involved. And they get downright irate when asked politely to engage in discourse with Randy until the sword-skeleton theory can be incorporated into the article without passing judgment.