There is a lot of hype around Web 2.0 these days (here is a great summary), and it's a difficult thing to get your arms around. Some analyst firms aren't ready to tackle the topic (I hope Burton changes their mind sooner rather than later), and they are perhaps following the leads of enterprises that haven't started exploiting it within. From a technology perspective, AJAX is a natural first play for enterprises wading into Web 2.0. But I believe that tagging could be the sleeper hit that enterprises should wake up to.
I have great respect for information architecture as a discipline and have worked and currently work with great IAs. But however skilled your IAs are, you will never please everyone. There are many different learning styles and conceptual approaches for content organization, and there is a great case to be made for users building their own organization for content, even if they don't "own" or manage it.
The best examples currently for tagging which many people are familiar with are del.icio.us and flickr. Another, even better in my opinion, implementation is last.fm (John, you rock for pointing me at this one!). Last.fm uses a fantastic AJAX implementation for tagging, so you don't even need to leave the content you are viewing to tag - very cool.
The greatest themes for Web 2.0 are participation and transparency, and all of these sites do that well. As you tag, you can see your own tags as well as what others are tagging the same thing. When you browse your tags, you can see what content others have tagged with those same tags. And finally, you can make your tags public so that others can see what you are doing.
Portals and content aggregation have been a big push in enterprises, but when there was content bloat the best initial answer was search engines - buy the best that you can afford. But turning your users into habitual search junkies isn't doing them any favors. Another thought is that you should never require users to find something twice your way - tagging gets you around that. They get to find it your way the first time, but then they tag it and find it their way next time.
I think tagging is the next Good Thing to come along in the world of content organization and it's time for it to pick up momentum within the enterprise.