Nice article! I was never unsure of the exact definition of Web 2.0, now I know its not very clear cut. Its more of a case-by-case basis whether something is web 2.0.
Just after a quick scan it looks like it was coined because of the dot com crash that happened and Web 2.0 seemed to fit. Still a lot of disagreement of what it means but google's web applications (online word, online speadsheet, etc, etc) in my mind is a good example of Web 2.0. A new mentality of what the web can do with no hard boundaries and the move from desktop applications to web applications (allows for mobility and freedom in computing).