Jimmy Wales and Larry Sanger co-founders in 2001, San Francisco CA
Wikipedia is a free, open content online encyclopedia created through the collaborative effort of a community of users who have contributed to its content. Anyone registered on the site can create an article for publication; registration is not required to edit articles. It is a wiki, a software program that enables anyone to edit Web site content through their Web browser.
Criticisms of Wikipedia include assertions that its openness makes it unreliable and unauthorative. Because anyone can edit any article, the site’s entries can be questionable.
Web 2.0: Who, What, Why, How 