I'm not sure what to say about tagging.Tags could be quite a useful system for libraries. It seems to be a good way of organising information, and as long as everyone's sensible about the tags they add then I can't see a problem with it.
Having had a look at the way Ann Arbour District Library uses tagging, I can see that it is a good way to organise things by using the terminology that readers are actually searching with. Terminology naturally changes over time and I think tagging in this way is a good method of keeping track of such changes.
However I think that there still is (and always will be) a place for standard terms, such as those used in LCSH.
