The semantic Web

This is in response to a discussion in #LAK11
The semantic web is an umbrella term for an initiative to make the web richer by attempting to tag large data collections with tags conveying their meanings and knowledge content.  In some sense I see it as being an outgrowth of the AI community's effort to encode knowledge into semantic maps.
I think its a wonderful project, but perhaps a little too ambitious, and I'll tell you why. Humans love to re-purpose things in unexpected ways, and I cant see a set of tags which would be broad enough to encompass all possible uses, yet retain enough specificity to be useful. As an example:
Once upon a time there was an astronomer who was looking at galaxies, and after two years of looking at galaxies everyday they asked for help:
http://en.wikipedia.org/wiki/Galaxy_Zoo
and currently
http://www.zooniverse.org/projects
Whats interesting in all of this is that:
1) These are collections of big data which still need many thousands of people to generate knowledge, and
2) A specific tool for a specific task, (deciding whether galaxies were spirals or not) is now looking for space junk on the moon, examining solar storms, and reading old ships logs to find out about global warming.
This is a very human thing to do, other examples, a website set up for selling Pez dispensers turned into Ebay, and a piece of software set up to help an academic keep track of references, turned into Google.
This is human.
At our best we look above and beyond.
 The second problem is the one alluded to in the old joke about the British and the Americans being two nations divided by a common language.
As a chemist I once studied a set of small molecules each containing 4 atoms.
I was talking to another computational chemist and they recommended a particular piece of software as being good for small molecules.
I tried it, and it failed.
When I met them again, I asked about it. It turned out that they were doing computational biochemistry, and small for them was around 10,000 or so atoms big. 
Even in very closely related fields terms can have very different meanings.
My 2c.
Laurence Cuffe