Besides having a clever title, this article (and associated comments) has some nice insights into the distinction between controlled vocabularies and folksonomies (hey, they’re not my terms, so don’t blame me). It’s very interesting to see what is emerging due to the popularity of folksonomy-based services right now.
I’m sure there’s lots of academic work in this area, too, although I haven’t looked at much of it. Hmm, it’s interesting, the difference between academic research and the emerging understanding from popular services is quite analogous to the difference between controlled vocabularies and folksonomies…