If you haven't heard, here's a success story about a Wikipedia vs. Britannica match-up. As a free online encyclopedia that anyone can edit, many have wondered how accurate it can be. A Nature study suggests, not bad!
Excerpt: "In the study, entries were chosen from the websites of Wikipedia and Encyclopaedia Britannica on a broad range of scientific disciplines and sent to a relevant expert for peer review. Each reviewer examined the entry on a single subject from the two encyclopaedias; they were not told which article came from which encyclopaedia. A total of 42 usable reviews were returned out of 50 sent out, and were then examined by Nature's news team. Only eight serious errors, such as misinterpretations of important concepts, were detected in the pairs of articles reviewed, four from each encyclopaedia. But reviewers also found many factual errors, omissions or misleading statements: 162 and 123 in Wikipedia and Britannica, respectively.
Internet encyclopaedias go head to head : Nature