Are you not quite sure O'Rielly's definition of Web 2.0 tells the whole story? Here are some further definitions for the curious investor:

The rebound of Web-based businesses after the dotcom bust, epitomized by perhaps thousands of start-ups.

A social movement in which everyone on the Web is able to create and share content.

A way to harness the collective intelligence of every Web user to create better products and services.

An environment of swift, continuous innovation that taps ideas from anyone who wants to contribute.