Upfront I must admit to being a code geek. Over the last 6-8 months I have been immersed in learning technologies that make the Web 2.0 experience possible. First, I must say this is some mighty cool stuff! I often find myself giddy with laughter when I figure out how to make a boring web page do my bidding. And yes, my wife often questions my sanity.
I recently had the opportunity to spec out a project requiring my new found knowledge. As the project owner and I went over the details I couldn't help feeling confused. After spending too much time sorting things out a reality hit - each of us had our own vision of what Web 2.0 consists of.
So I pose this simple question: What does Web 2.0 mean to you?

definition
My definition: On Web 2.0, application uses YOU!
Very difficult to define
Mike,
In conversations with IT folks, I find that this Web 2.0 term is not well understood. Some folks think of it as a new way to use the Web - i.e., a Web that is no longer just about publishing, but rather about interaction and self-expression. Some folks define Web 2.0 as the set of tools that make that possible. To me, the former definition is the more important. It's about how the Web becomes personal and self-expressive, truly interactive, rather than just a medium for consuming information.
JG
Power to the people
For me, Web 2.0 refers to a set of concepts that embrace the democratization of the web by giving people more control to author, modify, search, collect and disseminate content and knowledge. These concepts are rapidly evolving resulting in the daily appearance of new widgets, functions and delivery mechanisms. Confusing, you bet! Its easier to get agreement on the concepts, a bit more difficult to get agreement on the specifics.
That's my take, anyways!
I've never actually understood the need to label anything Web 2.0. It's the same internet it always was...the only thing which has changed is that people are using the internet for more things today than ever before. The code may be different, but the internet is still the internet.
Speaking on behalf of my generation, as a 23 year old, I've never heard another person my age (or thereabouts) use the term Web 2.0 in a meaningful way. I suspect many of us find the term unnecessary.
That's my take, anyways!
My answer to What Web 2.0 is
Here you can watch my organized analysis about What Web 2.0 is and my final address of this question.
What is Web 2.0? | The Path towards Next Generation, Series No.1
http://yihongs-research.blogspot.com/2007/10/what-is-web-20-path-towards-next.html
-- Yihong