What is Web 3.0?
I myself have on occasion used the term Web 3.0 to refer to social networking capabilities well beyond the usual Web 2.0 capabilities such as blogs, podcasts, AJAX programming, Flickr, etc., but the meaning is still up for grabs.
Some people are simply using it as a "version 2" of Web 2.0, or a Web 2.0 that really works and is user-friendly for normal people.
Some people are using Web 3.0 to refer to a much stronger sense of community than we get with a loose network of blogs.
Some people use Web 2.0 to refer to hard-core Semantic Web structures, possibly including artificial intelligence (AI).
Some refer to virtual worlds such as SecondLife.
Some traditionalists use Web 1.0 to refer to pre-ecommerce web sites, Web 2.0 to refer to ecommerce web sites (e.g., Amazon), and Web 3.0 to refer to a little bit more than what most people call Web 2.0 (more intensive collaboration.)
There is actually a Wikipedia article on Web 3.0.
There are a number of capabilities that I have been thinking about for future incarnations of the Web (e.g., a true Knowledge Web), but I honestly am not sure which subset makes sense for the near term Web 3.0.
I do recognize that I should consider the definition more carefully.
Maybe the right thing to do is to consider what might be part of Web 4.0 and use that boundary to define what is doable in the nearer term and call that Web 3.0.