Like it or loathe it, Wikipedia is a force. When contributors penned its new entry on Norwegian actress Beate Eriksen on Aug. 17, the English-language version of the controversial user-generated encyclopedia reached 3 million entries. More impressive still: more than 10 million users contributed to that milestone. Not bad for a service originally conceived as an afterthought to Nupedia, a failed first attempt by Internet entrepreneur Jimmy Wales and philosopher Lawrence Sanger at creating a free online encyclopedia.

When Nupedia was created in 2000, the plan was for it to feature expert-written, peer-reviewed content. But it suffered from a major problem: a lack of speed. In its first six months, only two articles made it through the process. To spur better production, Sanger suggested creating a counterpart that anyone could contribute to without editorial review. Wikipedia.com went live on Jan. 15, 2001, and the new model quickly eclipsed its older sibling. By the end of the first year, Wikipedia contained more than 20,000 articles in 18 languages. Since then, the site has grown rapidly, swelling to 250,000 articles by 2004 and a million by 2006. (See the 50 best inventions of 2008.)

Even in its earliest days, Wikipedia had to reckon with a slew of problems. Among them were vandalism and the lack of a fixed formula for determining what should and shouldn't be included in an encyclopedia unconstrained by physical limitations. The emerging community included a volunteer army of editors, who helped to keep the content aligned with Wikipedia's rules, the first version of which Sanger created in 2002. As the project grew, vandalization and dilution of the encyclopedia's content became more difficult to address. The site's software keeps a log of every modification to every page, and this tracking system has been used to bust some high-profile offenders. In May, Wikipedia banned IP addresses owned by the Church of Scientology on the grounds that Scientologists were making edits that didn't suggest a "neutral point of view"  the encyclopedia's golden rule.

But since its inception, the biggest issue dogging Wikipedia has been concerns about its accuracy. Sanger himself left Wikipedia in 2002 over questions about the legitimacy of the project's entries; he later established a competing encyclopedia, Citizendium, with more rigorous contribution criteria. While a 2005 study by Nature found that Wikipedia's science entries came close to matching the Encyclopaedia Britannica's in terms of accuracy  with 2.92 mistakes per article for Britannica and 3.86 for Wikipedia  no one argues that Wikipedia's content is flawless. Critics say the writing is clunky or prone to bias and that the authors focus on pet projects. Indeed, the site's list of Star Wars creatures totals more than 15,000 words, while the entire entry on World War II has just 10,000.

Running an organization as influential as Wikipedia isn't inexpensive. The company's costs reach nearly $6 million per year, and though it recorded more than 100 billion page views last year, the site has no advertisements. With that level of traffic, even a single text advertisement per page would net Wikipedia millions of dollars, but Wales is insistent that the service, which is supported by private donations, remains ad-free.

As impressive a milestone as 3 million articles is, it simply makes the English Wikipedia the largest component of a massive international enterprise. Wikipedia now contains more than 13 million articles in 271 different languages. The German-language version is the next largest, with more than 900,000 entries, but there's something for readers of every language. Even Cheyenne, which is spoken by only 1,700 Native Americans, has its own version of Wikipedia, although it boasts just 62 articles. Wales, who remains the "spiritual head" of the movement, says he wants Wikipedia to one day contain the sum of human knowledge. It has a way to go, but in just a few years the site has come closer to reaching that lofty goal than anything else.

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