Google CEO Eric Smidt has a definition for web 3.0 and it’s not so bad. ;o)
He calls web 2.0 a marketing term, which it obviously is!
He said that while Web 2.0 was based on Ajax, Web 3.0 will be “applications that are pieced together” – with the characteristics that the apps are relatively small, the data is in the cloud, the apps can run on any device (PC or mobile), the apps are very fast and very customizable, and are distributed virally (social networks, email, etc).
See his answer here: