There is a lot of disagreement about what the phrase Web 2.0 means. Let’s clear that up.
One answer is that Web 2.0 refers to the propensity of recent Internet applications to be more collaborative and provide for a richer user experience. Web1.0 was a Web site that looked like a brochure or a resume. Web 2.0 is a blog. Web1.0 was your newspaper’s classified ads, just webified. Web 2.0 is eBay or craigslist. Web1.0 was Netscape (i.e. here’s some software). Web 2.0 is Google (there’s nothing to install but it’s powerful).
Web 2.0 is about harnessing collective intelligence and eliminating the software release cycle – it’s about providing services, not products. It’s about trusting users as co-developers of content or even of technology. As an example, Amazon.com does this with its user review system.
A more cynical definition of Web 2.0, found in the blogosphere in Europe, (where they tend to be more conservative about technology) is