The Wikipedia is constantly edited by a wide variety of people with a wide variety of motives, and inevitably some are trying to subvert the integrity of the encyclopedia. Research suggests that, for the most part, these attacks are dealt with quickly.
The open nature of the editing model has been central to most criticism of Wikipedia. For example, a reader of an article cannot be certain that it has not been vandalized with the insertion of false information or the removal of essential information. Former Encyclopaedia Britannica editor-in-chief Robert McHenry once described this by saying:
The user who visits Wikipedia to learn about some subject, to confirm some matter of fact, is rather in the position of a visitor to a public restroom. It may be obviously dirty, so that he knows to exercise great care, or it may seem fairly clean, so that he may be lulled into a false sense of security. What he certainly does not know is who has used the facilities before him.and called Wikipedia a "faith-based encyclopedia."
John Seigenthaler has described Wikipedia as "a flawed and irresponsible research tool."In practice, vandalism is fairly easy to remove from wikis, and the median time to detect and fix vandalisms is typically very low, usually a few minutes, but in one particularly well-publicized incident, false information was introduced into the biography of American political figure John Seigenthaler and remained undetected for four months. John Seigenthaler, the founding editorial director of USA Today and founder of the Freedom Forum First Amendment Center at Vanderbilt University, called Jimmy Wales and asked him, "...Do you ...have any way to know who wrote that?" "No, we don't", said Jimmy.This incident led to policy changes on the site, specifically targeted at tightening up the verifiability of all biographical articles of living people.
Spam, agenda pushing, and trolls
Wikipedia's open structure inherently makes it an easy target for Internet trolls, spamming, and those with an agenda to push. The addition of political spin to articles by organizations including members of the U.S. House of Representatives and special interest groups has been noted, and organizations such as Microsoft have offered financial incentives to work on certain articles. These issues have been parodied, notably by Stephen Colbert in The Colbert Report.
For example, in August 2007, the website WikiScanner began to trace the sources of changes made to Wikipedia by anonymous editors without Wikipedia accounts. The program revealed that many such edits were made by corporations or government agencies changing the content of articles related to them, their personnel or their work.
The Wikipedia has a complex multi-layered defence against these kinds of attacks. These include users checking pages and edits, computer programs ('bots') that are carefully designed to try to detect them and fix them automatically (or semi-automatically), blocks on the creation of links to particular websites, blocks on edits from particular accounts, IP addresses or address ranges.
For heavily attacked pages, particular articles can be semi-protected so that only well established accounts can edit them, or for particularly contentious cases, locked so that only administrators are able to make changes.
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As an encyclopedia building project, Wikipedia seeks to create a summary of all human knowledge: all of topics covered by a conventional print encyclopedia plus any other "notable" (therefore verifiable by published sources) topics, which are permitted by unlimited disk space. In particular, it contains materials that some people, including Wikipedia editors, may find objectionable, offensive, or pornographic. It was made clear that this policy is not up for debate, and the policy has sometimes proved controversial. For instance, in 2008, Wikipedia rejected an online petition against the inclusion of Muhammad's depictions in its English edition, citing this policy. The presence of politically sensitive materials in Wikipedia had also led the People's Republic of China to block access to parts of the site. (See also: IWF block of Wikipedia)
Content in Wikipedia is subject to the laws (in particular copyright law) in Florida, where Wikipedia servers are hosted, and several editorial policies and guidelines that are intended to reinforce the notion that Wikipedia is an encyclopedia. Each entry in Wikipedia must be about a topic that is encyclopedic and thus is worthy of inclusion. A topic is deemed encyclopedic if it is "notable" in the Wikipedia jargon; i.e., if it has received significant coverage in secondary reliable sources (i.e., mainstream media or major academic journals) that are independent of the subject of the topic. Second, Wikipedia must expose knowledge that is already established and recognized. In other words, it must not present, for instance, new information or original works. A claim that is likely to be challenged requires a reference to reliable sources. Within the Wikipedia community, this is often phrased as "verifiability, not truth" to express the idea that the readers are left themselves to check the truthfulness of what appears in the articles and to make their own interpretations. Finally, Wikipedia does not take a side. All opinions and viewpoints, if attributable to external sources, must enjoy appropriate share of coverage within an article. Wikipedia editors as a community write and revise those policies and guidelines and enforce them by deleting, annotating with tags, or modifying article materials failing to meet them. (See also deletionism and inclusionism)