Jimmy Wales went from betting on interest rates and foreign-currency fluctuations (as an option trader) to betting on the willingness of people to share their knowledge. That's how Wikipedia, imagined in 2001, became one of the most-referenced, most-used repositories of knowledge on the planet, with more than four and a half million articles in English (compared with the Britannica's 80,000) and millions in dozens of other languages, all freely available.

The "wiki" in the name refers to software that allows anyone with Internet access to add, delete or edit entries. This has led to controversies about the reliability of the information, prompting the Wikimedia Foundation to set tighter rules for editors, while still keeping Wikipedia open-source. One thing is certain: Wikipedia will never be finished. In the meantime Wales has started working on Wikiasari, a wiki-style search engine.