To me that question is actually pretty simple, albeit the term “Web 2.0” probably causes more confusion than it should. This isn't really about a new version of the World Wide Web. It's not a version upgrade of some traffic management switches or software.
Web 2.0 is about new technologies that bring the web closer to people. It is about new way to create content and communicate with others. It is about new means for networking, collaboration and idea generation.
Web 2.0 is: this blog; my del.icio.us bookmark collection; Wikipedia and Google docs for collaborative creation; Flickr managing images online; etc. If you have better examples, please share them with me.
Web 2.0 is the evolution of participation on the web.
A week-long dialogue took place 21-28 September 2007 focused on the use of information, communication, and associated technologies in sustainable agricultural development and food security. Known as "e-Agriculture week", this unique event included the Web 2.0 for Dev conference that opened with “The Machine is Us/ing Us”. If you have not seen this video clip, take 5 minutes and watch it on YouTube. It’s a great opener to these exciting and ongoing developments.
BTW, I've got a lot more to say about e-agriculture soon...