Actually, the real definition of web 2.0 has nothing to do with design - rather, simple design is a product of web 2.0 which really refers to community and user generated content functionality.
Glossy reflections and stupid things like that (which by the way is outdated) is just people who saw simple websites (because simplicity increases functionality) and tried to make them more graphic intensive without making them graphically heavy.
One thing you'll notice about the list Rekhyt wrote is that all of them are community based websites where users generate the content in an easy-to-use way.
Making a static page with big reflections and shiny graphics is NOT web 2.0. Unfortunately the real definition is continuing to change and will eventually mean nothing if people keep misusing it. There are many many design trends out there, don't make "web 2.0" just another one of them.