Dead 2.0 has an interesting post on "what is tagging?". Here's Dead's Mom:

O.K. On del.icio.us/tag/tagging it basically talks about the same stuff all over again, i.e. Because everyone else is doing it too, LibraryThing connects you with people who read the same things. I have to say… I don’t have enough time in my life to spend with (mostly) idiots who think that what they have to say has enough relevance and importance that I would want to waste my time in their lives. I find my life rewarding and challenging enough!

It's overlooked that tags don't have meaning outside of their social context: i.e. it's either myself (i.e. my tags) or my community (people doing stuff similar to me) that will produce tags useful to me. This is why I like tags in the context of Enterprise 2.0/Enterprise Datasphere: we're talking about a community of individuals that inherently have a common interest.

Dead's Mom also takes on Tag Clouds:

I just went back to del.icio.us.tag. I get that certain words are highlighted, I get what this means, what I don’t get is the relevance in my world.

I kind of agree with this too, which is why there isn't a generic "everyone" tag cloud on this site: I just don't see the utility besides "me too". What would be interesting (maybe) is a tag cloud about what everyone else is doing filtered by my tags. That might work.