How do you enable "the wisdom of crowds"? Part of the power of community is that a group of people can solve problems much more easily than individuals, but only if you can provide tools that make it possible for them to do so and appeal to their own interests.
Derek Powazek has an interesting post over on A List Apart that details some of the components necessary for "a crowd to be wise." According to Powazek, you have to have simplicity, a clean interface, aggregation, and a group of people who are thinking about their own needs:
It’s counter-intuitive, but the wisest crowds are the ones made up of individuals who are thinking about their own needs, not the needs of the group. In the stock market, the participants are all motivated to buy low and sell high. Yet the markets are usually wise about finding the value of a company. Each person is thinking about their bottom line, not the health of the company or the market, but it works.
Similarly, website creators were not consciously voting for certain sites to be highly ranked, but the collective linking decisions did produce wise results. Nowadays, link spammers do try to manipulate Google’s results, which is akin to stock manipulation. Both practices are fought by the institutions that depend on unmanipulated results.
Altruism is all well and good, but people are usually much more motivated by their own interests than the interests of others. This is one reason why open source code is usually so much better than the documentation that accompanies it (unless someone is paid to produce the docs): People contribute code because they want to use the code. People write open source documentation, typically, for altruistic purposes. Which is why many documentation projects flounder -- the documentation does the writer little to no good, as they're unlikely to read it again.
Code, however, is continually useful, because it's often produced for "selfish" purposes.
If you're wondering how to drive participation in a project: Whether it's an open source project, a collaborative Web site, or some other endeavor don't think about what's in it for you: Think about what's in it for them. When you can find a way to let the crowd scratch their own itches, and provide the necessary tools to do so, you're on the road to success.