The Wikipedia article (http://en.wikipedia.org/wiki/Web_2.0) talks more about technology, but I think people are really at the center here - data yes, but knowledge, experience, connections, community and passions more so. Mashups on the service layer are often the primary feature used in describing it, but this is really not the core idea in my mind. Many people cite Ajax styled interfaces as the key component, but the UI layer only has value when applied appropriately to a problem such as the housing maps example.

I think a lot of people are still missing the main point here - the real differences that delineate this era are open standards, connectivity, collaboration, community, consumer as producer of media AND the browser as rich/robust interface. While it is certainly the characteristics of the technology that define it in a lot of discussions today, I think it is really deeper than that.

It would seem that the mass media and big money have really co-opted the core idea and what it really means is still to be determined. That is why I think coming together to define this wave in terms of Web 2.1 is really important at this time - what do we, the creators and users really want it to be?