Web 2.0?

Do people really know what web 2.0 is?
This is rather a curiosity on my part rather than an attempt at a serious debate.
I’ll be interested to know if anyone’s initial perception changes after looking into it.
The best point of reference is probably this article by O’Reiley
http://www.oreillynet.com/pub/a/oreilly/tim/news/2005/09/30/what-is-web-20.html
It is actually quite an interesting article even if you are not that into technology.