I've never been fond of the term "Web 2.0" - in part because it's often used to imply a new suite of technologies even though it's largely founded on concepts that have been well-established (but not widely-utilized) for over a decade. For example, XMLHttpRequest - the backbone of the AJAX style of development - first shipped with Internet Explorer 5.0 in 1999. The term thus struck me as another example of the popular trend in software of rebranding old technologies as the "next big thing".