The BBC are trialling the use of 'tagging' on their new England message board. Indeed, the front page of the messageboard includes a tagcloud.
One of the key reasons that tagging was developed is because with English regions, conversations often spill into other regions, and pidgeonholing users and conversations into seperate, discrete boards is always going to be contentious. (Not least when it comes to Cornwall...)
As technical developer Jim Lynn explains on a DNA Hub thread, "it is only a beta because we need to see if it works well. And ... the only way to find that out is to actually use it for real."
Crucially, though, the tagging functionality hasn't yet been opened to the public, and currently only hosts can tag. BBC staffer Peta explains that "the intention, if all goes to plan is to introduce public tagging at some point in the future." This being the BBC though, there's the whole moderation issue to think about. "We'd have to enable a swear filter on the tagging system first, or some bright spark would inevitably find the temptation too hard to resist! I'd hope that it could at least be rolled forward with a volunteer group of 'trusted taggers' at some point in the not too distant future, once the initial concept has proved itself."
By the looks of things so far, they've gone for a shallow 'folksonomy' (see explanation) which is probably simpler for users to 'get' and makes for a more definative set of tags for any single thread. However it may also lead to conflicts which wouldn't be apparent if a broad folksonomy were to be used. There may be arguments over whether it is 'right' that a thread should be tagged 'Celtic' or not, for example, and complaints of over 'crossthreading' if one thread is tagged with a huge list of regions so that it appears in all the default region views...
If a broad folksonomy were adopted, an individual could use their own volcabulary without it imposing on the group, and you could aggregate the tags in a more sophisticated way (ie if 10 people have tagged a thread 'Cornwall' it might appear higher than a thread which only 2 people have tagged 'Cornwall'). The only problem with using a broad folksonomy is that is might be more difficult to communicate to users, and there would need to be a greater payback to encourage users to tag... (one of which might be a view that shows your own most-used and most-read tags)
Either which way, it will be an interesting experiment...