Tim O’Reilly notes the heart of Web 2.0:
Whether it’s pagerank at Google, interestingness at Flickr, or diggs, or SmugMug’s most popular feature, we see all across the web attempts to incorporate human intelligence into web applications. As I’ve written many times, harnessing collective intelligence is the very heart of Web 2.0. And that intelligence is distinguished by its bionic nature: we’re building applications that are a fusion of human and machine.