Wikipedia, the user-created encyclopedia with no central editor, became a surprising triumph over the early 2000s, drawing on the labor mainly of obsessive young men interested in making relatively anonymous contributions to a larger project. But unlike Google and others, when Wikipedia came to its own fork in the road, gaining enough traffic to rival or exceed that of nearly any other site, save the search engines, it chose the other path; deciding to remain free of advertising, it effectively forsook billions in potential revenue. The founder, Jimmy Wales, officially explained the decision as follows: “I think of Wikipedia as I do a library or a school—and commercial advertising is not right in that space….Maximizing revenue is not our goal.”

Tim Wu, The Attention Merchants, loc. 912