Wikipedia is a Web-based free content encyclopedia that is openly edited and freely readable. It has 187 independent language editions sponsored by the non-profit Wikimedia Foundation. Entries on traditional encyclopedic topics exist alongside those on almanac, gazetteer and current events topics. Its goal is to create “a world in which every single person on the planet is given free access to the sum of all human knowledge.” Wikipedia is one of the most popular reference sites on the Web, receiving around 50 million hits per day.
Amazingly, no one is paid to edit this online encyclopedia which already weighs in as twice as big (in number of words) as the Encyclopedia Britannica. All the entries are written and fact-checked by the readers. Seems like it’d be the worse source of information on the planet; because it’s open-source, it’s not. Anyone can challenge and correct any entry, so the finished results tend to be extremely factual and areas of disagreement are well-marked.
Here’s what Jimmy Whales said about accuracy:
… the average quality of entries is high, but any given page could be broken at any moment. IBM did some research on Wikipedia, and it found that for certain types of vandalism, the median time to correction is under five minutes. That’s for the typical type of change, when someone blanks out a page or puts in a curse word.