Everyone's been talking about Web 2.0 for a while now, and I still get the feeling no-one really knows what it is. I think Stephen Fry's description of web 2.0 as "genuine interactivity, if you like, simply because people can upload as well as download." comes close to my understanding of the phenomena... but that's not really the point. The point is, "web two point oh" sounds cool. Tim O'Reilly probably knew this when he coined the phrase. People and companies want web 2.0, despite the fact that they're not really sure what it is, because it sounds cool.
On the one hand, we have web 2.0 mash-ups and tag clouds and Ajax and all that lovely interactive multimedia goodness. On the other hand, we have web standards. Standards are not as cool as Web 2.0. They sound a bit... boring, frankly (and the W3C spec documents really don't help with this. Informative, yes - but readable?) Many companies would rather spend their time and money investing in potential revenue sources instead of the endless hours of testing and tweaking that's involved in getting semantically clean, standards-compliant pages that look good and work across all modern browsers... and as soon as they want something clever and interactive, they reach for Flash.
IE8 is coming, and will supposedly offer the standards support that we've all been waiting for. Joel Spolsky has written this post about the fact that there really isn't an acceptable compromise between standards compliance and backward compatibility. Either you follow the standards and break old sites, or you maintain bugwards compatibility at the expense of standards compliance.
When you say "IE8's default rendering view conforms to the W3C XHTML+CSS standards", people yawn. I mean, c'mon. Double-you-three-ex-aitch-cee-ess-what?
So how about if we just take a reasonable baseline set W3C guidelines - XHTML 1.1, CSS 2.1, XmlHttpRequest - and say that "Web 3.0" means full, complete support for those standards? It could be that simple. IE8 can be a Web 3.0 browser. Firefox 3 can be a Web 3.0 browser; Opera 10 can be a Web 3.0 browser (if Opera 9 isn't already, that is). Google SpacePirate or whatever they think of next will be a Web 3.0 application, which works as intended on any web 3.0 browser. Technically, it's exactly the same as what's going on right now - but I wonder what'll happen if we slap a cool name on it and make standards sound like the Next Big Thing?