Beans, Blogs, and Feeds
Four basic conditions? That's all you got, Surowiecki? Your conditions have just met their match: bloggers are a wise crowd.
Diversity of opinion - That's a no-brainer. Bloggers publish hundreds of thousands of posts daily, each one charged with its author's unique opinion.
Independence of members - Except for your friends saying "You've got to blog about that!" bloggers are not controlled by anyone else.
Decentralization - There is no central authority in the blogosphere; publish your blog anywhere you want with any tool you want.
A method for aggregating opinions - Blog feeds make aggregation a snap and there is no shortage of services that take advantage of that fact.