Last year , however, a study in the journal Nature compared Britannica and Wikipedia science articles and suggested that the former are usually only marginally more accurate than the latter. Britannica demonstrated that Nature's analysis was seriously flawed (“Fatally Flawed” was the fair title of the response), and no one has produced a more authoritative study of Wikipedia’s accuracy. Yet it is a widely accepted view that Wikipedia is comparable to Britannica. Vandalism also has proved much less of an issue than originally feared. A study by IBM suggests that although vandalism does occur (particularly on high-profile entries like “George W. Bush”), watchful members of the huge Wikipedia community usually swoop down to stop the malfeasance shortly after it begins.
But early in 2007, something strange happened: Wikipedia's growth line flattened. People suddenly became reluctant to create new articles or fix errors or add their kernels of wisdom to existing pages. "When we first noticed it, we thought it was a blip," says Ed Chi, a computer scientist at California's Palo Alto Research Center whose lab has studied Wikipedia extensively. But Wikipedia peaked in March 2007 at about 820,000 contributors; the site hasn't seen as many editors since. "By the middle of 2009, we realized that this was a real phenomenon," says Chi. "It's no longer growing exponentially. Something very different is happening now." See the 50 best websites of 2009.
What stunted Wikipedia's growth? And what does the slump tell us about the long-term viability of such strange and invaluable online experiments? Perhaps that the Web has limits after all, particularly when it comes to the phenomenon known as crowdsourcing. Wikipedians — the volunteers who run the site, especially the approximately 1,000 editors who wield the most power over what you see — have been in a self-reflective mood. Not only is Wikipedia slowing, but also new stats suggest that hard-core participants are a pretty homogeneous set — the opposite of the ecumenical wiki ideal. Women, for instance, make up only 13% of contributors. The project's annual conference in Buenos Aires this summer bustled with discussions about the numbers and how the movement can attract a wider class of participants.
At the same time, volunteers have been trying to improve Wikipedia's trustworthiness, which has been sullied by a few defamatory hoaxes — most notably, one involving the journalist John Seigenthaler, whose Wikipedia entry falsely stated that he'd been a suspect in the John F. Kennedy and Robert F. Kennedy assassinations. They recently instituted a major change, imposing a layer of editorial control on entries about living people. In the past, only articles on high-profile subjects like Barack Obama were protected from anonymous revisions. Under the new plan, people can freely alter Wikipedia articles on, say, their local officials or company head — but those changes will become live only once they've been vetted by a Wikipedia administrator. "Few articles on Wikipedia are more important than those that are about people who are actually walking the earth," says Jay Walsh, a spokesman for the Wikimedia Foundation, the nonprofit that oversees the encyclopedia. "What we want to do is find ways to be more fair, accurate, and to do better — to be nicer — to those people."
Yet that gets to Wikipedia's central dilemma. Chi's research suggests that the encyclopedia thrives on chaos — that the more freewheeling it is, the better it can attract committed volunteers who keep adding to its corpus. But over the years, as Wikipedia has added layers of control to bolster accuracy and fairness, it has developed a kind of bureaucracy. "It may be that the bureaucracy is inevitable when a project like this becomes sufficiently important," Chi says. But who wants to participate in a project lousy with bureaucrats?
There is a benign explanation for Wikipedia's slackening pace: the site has simply hit the natural limit of knowledge expansion. In its early days, it was easy to add stuff. But once others had entered historical sketches of every American city, taxonomies of all the world's species, bios of every character on The Sopranos and essentially everything else — well, what more could they expect you to add? So the only stuff left is esoteric, and it attracts fewer participants because the only editing jobs left are "janitorial" — making sure that articles are well formatted and readable.
Chi thinks something more drastic has occurred: the Web's first major ecosystem collapse. Think of Wikipedia's community of volunteer editors as a family of bunnies left to roam freely over an abundant green prairie. In early, fat times, their numbers grow geometrically. More bunnies consume more resources, though, and at some point, the prairie becomes depleted, and the population crashes.
Instead of prairie grasses, Wikipedia's natural resource is an emotion. "There's the rush of joy that you get the first time you make an edit to Wikipedia, and you realize that 330 million people are seeing it live," says Sue Gardner, Wikimedia Foundation's executive director. In Wikipedia's early days, every new addition to the site had a roughly equal chance of surviving editors' scrutiny. Over time, though, a class system emerged; now revisions made by infrequent contributors are much likelier to be undone by élite Wikipedians. Chi also notes the rise of wiki-lawyering: for your edits to stick, you've got to learn to cite the complex laws of Wikipedia in arguments with other editors. Together, these changes have created a community not very hospitable to newcomers. Chi says, "People begin to wonder, 'Why should I contribute anymore?'" — and suddenly, like rabbits out of food, Wikipedia's population stops growing.
The foundation has been working to address some of these issues; for example, it is improving the site's antiquated, often incomprehensible editing interface. But as for the larger issue of trying to attract a more diverse constituency, it has no specific plan — only a goal. "The average Wikipedian is a young man in a wealthy country who's probably a grad student — somebody who's smart, literate, engaged in the world of ideas, thinking, learning, writing all the time," Gardner says. Those people are invaluable, she notes, but the encyclopedia is missing the voices of people in developing countries, women and experts in various specialties that have traditionally been divorced from tech. "We're just starting to get our heads around this. It's a genuinely difficult problem," Gardner says. "Obviously, Wikipedia is pretty good now. It works. But our challenge is to build a rich, diverse, broad culture of people, which is harder than it looks."
Before Wikipedia, nobody would have believed that an anonymous band of strangers could create something so useful. So is it crazy to imagine that, given the difficulties it faces, someday the whole experiment might blow up? "There are some bloggers out there who say, 'Oh, yeah, Wikipedia will be gone in five years,'" Chi says. "I think that's sensational. But our data does suggest its existence in 10 or 15 years may be in question."
Ten years is a long time on the Internet — longer than Wikipedia has even existed. Michael Snow, the foundation's chairman, says he's got a "fair amount of confidence" that Wikipedia will go on. It remains a precious resource — a completely free journal available to anyone and the model for a mode of online collaboration once hailed as revolutionary. Still, Wikipedia's troubles suggest the limits of Web 2.0 — that when an idealized community gets too big, it starts becoming dysfunctional. Just like every other human organization.