Something paradoxical is happening on the Web: just as digitization projects are making available terabytes of expert knowledge, previously tucked away in books and journals, more and more Web users are turning to each another instead of published sources for answers about everything.

In other words, the “social” Web is laying siege to traditional notions of authority and credibility. The editors of the Encyclopaedia Britannica, for instance, took a blow last year when a study in Nature purported to show that Britannica was only marginally more accurate than Wikipedia, the online encyclopedia cooperatively written and edited by almost 1.7 million registered users, who have created 4.7 million pages in dozens of languages and made 63 million edits.

Unlike Britannica articles, which are written by experts and thoroughly vetted, Wikipedia entries are reviewed only by other Wikipedia volunteers, which means there’s no guarantee of accuracy. Yet that doesn’t stop search engines such as Google from listing Wikipedia entries as the top search results for many factual queries. And it doesn’t stop millions of people from visiting the site – it’s the 16th-most trafficked destination on the Web, according to traffic-monitoring service Alexa, well ahead of news sites like CNN.com.

But who are the individuals contributing all this free content? And why do they do it? Although “user-generated content” is quickly becoming the mainstay of large Internet enterprises, from MySpace to Yahoo, the bulk of their content comes from people who often have no formal qualifications – and who don’t earn a dime in the process.

Yahoo Answers has its own fast-growing collection of user-contributed information on questions from the everyday to the arcane. The service, which became official in May, after months of beta-testing, lets registered users pose questions, post answers, search for previous answers, and vote for the best answers to some questions. As part of the Yahoo.com domain – the busiest on the entire Web – the service draws many visitors from other Yahoo properties, including search result pages, which often include links to top-rated answers (see “Yahoo’s Web 2.0 Overhaul”). Yahoo Answers had 9.1 million unique users as of May, according to Web tracking service Comscore/Hitwise, and featured 20 million answers in English and another 50 million in other languages.

To find out what motivates the most prolific contributors to social media sites like Yahoo Answers, Technology Review spoke with one of the site’s highest-rated writers, Emily Fontes. A contributor to the pregnancy and parenting category, Fontes teaches classes in the Seattle area on pregnancy and infant care during the early postpartum period. She’s also a “doula,” someone who provides mothers with emotional support and advice during childbirth. As of June 26, Fontes had authored 404 answers on Yahoo Answers, a high proportion of which were designated by other users as the best answer to a question.

Technology Review: How did you come across Yahoo Answers? What inspired you to start contributing, and what do you get out of it?

Emily Fontes: I started using the site in January. I’d been working at a pregnancy resource center for about three years. It’s one of my passions to work with pregnant women. I found [Yahoo Answers] to be another way to reach out to them. When I first found the site, I was immediately drawn to the “pregnancy and parenting” section. It’s hard to say that I get anything out of it other than helping people who need factual information I have.

TR: How much time do you spend answering questions at Yahoo Answers, and how do you choose which questions to answer?

EF: I’ve cut back a lot. I used to spend a whole lot of time, but now I probably spend about an hour in the evening. During that hour I usually only hit between four and five questions. I am not a “serial” answerer. I only take the time to answer questions that I’m really going to answer well. I don’t want to give one-sentence answers to 20 questions. I’d rather give two-paragraph answers to two questions. And if I come across a question that’s already been answered very well, I might not take the time to answer it. I’m really searching for a question that has not been answered well.

TR: There’s an elaborate system on Yahoo Answers for askers and general readers to rate the quality of answers. For most questions, a “best answer” is eventually chosen, either by the asker or a vote from general readers, and the person who wrote it gets a certain number of points. Do you consciously write your answers aiming for them to become best answers?

EF: Absolutely. My goal is “Best Answer” every time. I’m not so much concerned about how many points I have, or how high I am on the leader board for my category. I’m more concerned about what my percentage of best answers is – the percentage of all of my answers that are chosen as the best answer. I’m at 75 percent right now, which is one of the highest I’ve seen.*

TR: With Yahoo Answers, as with Wikipedia, there are very few controls on who gets to contribute – which means that even someone who is totally misinformed about a subject can post an answer that might look authoritative. Do you ever find yourself writing answers that specifically challenge or correct other people’s answers?

EF: Yes, I do, especially when they are about things in pregnancy that could affect someone’s health. Sometimes people are just being really silly and flippant. Those, you can ignore. But when people are seriously giving an answer that is incorrect and could be construed as correct, I’m really careful not only to rebut them but to give sources that back up my rebuttal.

TR: What’s your overall impression of the accuracy of the answers on Yahoo Answers?

EF: For the most part, I think everything balances itself out really well. For the answers I see where there is incorrect information, I am usually not the only person who comes back and says “That is incorrect.” The people who give bad information are balanced out by people who are professionals who know what they’re talking about, and who give good sources. For the most part, the thing that makes a best answer best is that the answerer gives really good sources.

TR: Yahoo Answers is unlike Wikipedia in the sense that once you’ve written an answer, other people can rebut it, but they can’t rewrite it. On Wikipedia, however, anything you write can be edited or deleted by other contributors. Would you feel comfortable sharing your knowledge in that context?

EF: I’m not a big fan of Wikipedia. I like Yahoo Answers for the fact that what I write is permanent. I don’t want something I’ve written to be edited and then construed as my own opinion. I just think there’s too much margin for error there. But I can see where Wikipedia is a valuable part of the Web community as well. I like the fact that things are so well organized [on Wikipedia] – whereas Yahoo Answers is harder to search.

TR: Being a health-care expert and provider, do you ever worry about your legal liability if an answer you write happens to be inaccurate, and someone claims they’re harmed by that?

EF: It always is a concern. Because that is what I do in my professional life as well, I teach childbirth classes, it’s really important for me to give an answer that could not possibly be thrown into debate or show me in a negative light. Again, the best way to avoid that is to give solid resources.

* Correction, 12:00 pm 6/27/06: Due to a typographical error, Ms. Fontes’ “best answer” percentage was originally given as 7 percent. It is 75 percent.