Most criticism of Wikipedia has been directed toward its content, community of established users, and processes. Critics have questioned its factual reliability, the readability and organization of the articles, the lack of methodical fact-checking, and its political bias. Concerns have also been raised about systemic bias along gender, racial, political, corporate, institutional, and national lines. In addition, conflicts of interest arising from corporate campaigns to influence content have also been highlighted. Further concerns include the vandalism and partisanship facilitated by anonymous editing, clique behavior (from contributors as well as administrators and other top figures), social stratification between a guardian class and newer users, excessive rule-making, edit warring, and uneven policy application.
The reliability of Wikipedia is often questioned. In Wikipedia: The Dumbing Down of World Knowledge (2010), journalist Edwin Black characterized the content of articles as a mixture of "truth, half-truth, and some falsehoods". Oliver Kamm, in Wisdom?: More like Dumbness of the Crowds (2007), said that articles usually are dominated by the loudest and most persistent editorial voices or by an interest group with an ideological "axe to grind".
In his article The 'Undue Weight' of Truth on Wikipedia (2012), Timothy Messer–Kruse criticized the undue-weight policy that deals with the relative importance of sources, observing that it showed Wikipedia's goal was not to present correct and definitive information about a subject but to present the majority opinion of the sources cited. In their article You Just Type in What You are Looking for: Undergraduates' Use of Library Resources vs. Wikipedia (2012) in an academic librarianship journal, the authors noted another author's point that omissions within an article might give the reader false ideas about a topic, based upon the incomplete content of Wikipedia.
Wikipedia is sometimes characterized as having a hostile editing environment.