From Mark Pesce's Hyperpeople blog:
Earlier this year, I was privileged to go “on tour” with Jimmy “Jimbo” Wales, the founder and public face of Wikipedia, as we crisscrossed the nation, talking to educators in Adelaide, Perth, Sydney and Melbourne. Everywhere we went, people asked the same question: why is Wikipedia such a success, while my wiki languishes? What do you need to achieve critical mass? The answer, Jimmy said, is five people. Five individuals dedicated to an altruistic sharing of collective intelligence should be enough to produce a flowering similar to Wikipedia. Jimbo has learned, through experience, that the “minor” language versions of Wikipedia (languages with less than 10 million native speakers), need at least five steady contributors to become self-sustaining. In the many wikis Jimbo oversees through his commercial arm, Wikia, he’s noted the same phenomenon time and again. Five people mark the tipping point between a hobby and a nascent hyperintelligence.I suspect this observation applies to a much wider array of networked activity than just wikis...