Web 2.0 is a metaphor to describe the evolution of web technology, philosophy, and human interaction that is sweeping the internet. Yes, it was a name for a conference, and a marketing term, but the term has become useful in describing a multi-faceted set of conditions that fall into a distinguishable construct. Its much easier than saying "The social- web - peer-to-peer - ajax - rss - mashup - collaberative- thing". Just like it's easier to say "The Bible" than say "The collection of books written over thousands of years in different languages...etc.". I'm sure it will go away, like "Information Super Highway" did. It's short, easy to spell and if the next wave is call Web 3.0 then I'm good with that too...