The Wikipedia page for Web 2.0 continues to evolve. It still doesn't read well in places, but some parts hit the mark. For example this is a pretty good explanation of the transition from Web 1.0 to Web 2.0:
"The original conception of the web (in this context, labeled Web 1.0) comprised static HTML pages that were updated rarely, if at all. The success of the dot-com era depended on a more dynamic web (sometimes labeled Web 1.5) where content management systems served dynamic XHTML web pages created on the fly from an ever-changing content database. In both senses, so-called eyeballing was considered intrinsic to the web experience, thus making page hits and visual aesthetics important factors.
Proponents of the Web 2.0 approach believe that web usage is increasingly oriented toward interaction and rudimentary social networks, which can serve content that exploits network effects with or without creating a visual, interactive web page. In one view, Web 2.0 sites act more as points of presence, or user-dependent web portals, than as traditional websites."
I don't think I've ever heard the term "Web 1.5" before, but nevermind... I still think the 'Business Impact' section of the Wikipedia definition needs a lot of work and I'm not sure the explanation of how Web 2.0 relates to the Semantic Web is quite right yet.
If I may give you the Crude Version of how I define Web 2.0 and the Semantic Web. Web 2.0 is 'The Web as Platform' and the Semantic Web is 'The Web of Meaning'. That's boiling it down to its essence, in order to make the point that they are two different concepts. I don't necessarily see Web 2.0 as an evolutionary stage towards the xanadu that is the Semantic Web (to mix my Web metaphors). There is a relationship there, don't get me wrong, but it needs to be fleshed out some more.
On this subject, this week I finished co-authoring an article for Digital Web Magazine about how Web 2.0 impacts the field of web design. I co-wrote it with Joshua Porter and hopefully it'll be published soon.
Once the Digital Web article comes out, I may have a go at editing the Wikipedia. I think we're getting closer to pinning down the definition of Web 2.0 - as always on the Web, it's being bootstrapped by the community as we go along :-)
p.s. I wish the Wikipedia had RSS feeds so we can easily track changes to pages!