What the hell is Web 2.0? Not even Wiki gives a clear answer.

It's "modern web development" using and "getting" the social side of the web, as well as technologies/ approaches such as blogs, wikis, tag clouds, contextual, collaborative, shared, fresh design, RSS, Ajax, etc. The buzzword itself is more of an "if you don't understand it already it's impossible to explain and to understand it you gotta live it" kind of thing, and you can use and abuse it for everything you want, but in the end it's just that: the latest iteraton of the "Web" with a couple of new features. Just as Web 3.0 will be a new iteration, with even more new features.