Web 2.0 embraces an architecture of participation—a design that encourages user interaction and community contributions.
Many Web 2.0 companies are built almost entirely on user-generated content and harnessing collective intelligence. The significance is not just in having user-generated content, but in how it is used. Google—the leading search engine and Internet advertising company—sends its users to user-generated websites by considering what users collectively have valued in the past. For websites like MySpace®, Facebook®, Flickr™, YouTube and Wikipedia®,users create the content, while the sites provide the platforms. These companies trust their users—without such trust, users cannot make significant contributions to the sites.
Web 3.0, aka Semantic web, will be the next step , and already we see the first hints of the semantic web in the mainstream: the photo tagging feature on Facebook is a great example. You upload a photo, tag the photo with your friend’s name, and Facebook automatically notifies that person that there’s a new picture of them in your photo album. It’s a lightweight vision of the future, where the context adds value.