Browsing the web looking for something totally different subject at the beginning, I ended up on the blog of (Jaanus, http://www.jaanuskase.com/en/2007/05/) and found the following video of a conference of David Weinberger called everything is miscellaneous. 

It is a very interesting and entertaining introduction on folksonomy.  If you think that the Wikipedia definitions are a bit dry (http://en.wikipedia.org/wiki/Taxonomy), have a look at this video; Mr Weinberger is a great speaker. It might help to understand the concepts used within TagandFacet, when the definitions of Wikipedia might be a bit dry.

I am still, amazed, everyday how internet, blogs can reduce the distance. Not even more than five years ago I wouldn't have been able to view this presentation or even less to share it.