What makes Wikipedia remarkable is that you can type in almost any word or subject in the English language and wind up with an article displayed on your computer screen in a fraction of a second. There's no jaunt over to the bookshelf and no shuffling through indexes and cross-references to find a nugget of knowledge. What's more, Wikipedia's million-plus articles in English eclipses Britannica's 80,000, Columbia's 51,000, and Encarta's 63,000. Even more mind-boggling is the fact that Wikipedia adds somewhere around 2,000
entries a day.

Of course, quantity and ease of use don't necessarily equate to quality. Some people, including Joel Waldfogel, Ehrenkranz Professor of Business and Public Policy at the Wharton School of the University of Pennsylvania, question how effectively a spirited cadre of volunteers can produce articles compared to top professionals and luminaries. For instance, Britannica boasts entries from Carl Sagan, Milton Friedman, and numerous Nobel laureates. World Book verifies any fact appearing in any article with at least three respected sources - not including other encyclopedias.

By comparison, Wikipedia is a virtual free-for-all, with more than 13,000 participants churning out articles. If you're inclined to add your two cents' worth, you simply click on a tab at the top of any entry that reads "Edit this page." You make desired changes and click "Save page." Your words are then visible for the entire world to see - though "page patrollers" dutifully track changes (another tab displays the entire history of an article) and verify that the information is appropriate and correct. They also undo vandalized pages - usually within five minutes, Wales says.