Assigning a discrete version number to the web seems to completely miss the point of the evolutionary, organic growth of the World Wide Web that the "2.0" moniker is ostensibly trying to describe. It presumes that there was a clear-cut switch from the "1.0" web and the "2.0" web. There wasn't. That doesn't even make sense: the web isn't some singular entity that is being released by a central authority with new features on a periodic basis. Implying as much just demonstrates you don't know how the web works.
It is the web. There was no 1.0, there is no 2.0, there will never be a 2.1 or 3.0 or whatever. Any more so than there was a life 1.0, life 2.0, life 2.1 or whatever (Second Life jokes aside). Calling it "web 2.0" is the moral equivalent of intelligent design for the Internet. Sure, there are standardization bodies for the protocols the web is built on, but do you really believe the modern web itself can be "best explained by an intelligent cause, not an undirected process such as natural selection"? I don't think so.
This has been out for a few months now, but if you haven't already seen it, a group of Kansas State University students put together a movie that describes the current state of evolution of the web:
Unfortunately, they make the mistake of attaching the 2.0 misnomer to the web. Which is truly a shame since they seem to "get it" in all other respects. The web is us and the last time I checked, there was no us 2.0.