While I don't line up with with the total web 2.0 labeling, Tom Scott has a great article that outlines some evolutionary changes in considering web development. As he points out "Site owners effectively thought of their sites as silos - a self contained object, a web of pages, with a handful of doors (links) in and out - well even if they didn’t think of them as silos they sure treated them as such. But as Tom Coates puts it Web 2.0 is about moving from a “web of pages to a web of data"