Via Robin Good, I get this article: Folksonomies: power to the people by Emanuele Quintarelli.

A folksonomy is a user-generated classification, emerging through bottom-up consensus. A fusion of the words folks and taxonomy, the first use of the term folksonomy has been attributed to Thomas Vander Wal. Taxonomy comes from taxis and nomos (from Greek). Taxis means classification. Nomos (or nomia) means management. Folk is people. The term was coined in the AIfIA mailing list to mean the wide-spreading practice of collaborative categorization using freely chosen keywords by a group of people cooperating spontaneously. Folksonomies are not a theory or a top-down strategy: they were born out of a feature (folk classification tools) introduced by software like Del.icio.us, Flickr, 43things, Furl, Technorati, etc. and from people using these platforms to tag their contents (links, photos, etc).

Here are some sections of the article: Limits of taxonomies, Folksonomies: an emerging approach to distributed classification, Folksonomies at work, Properties of folksonomies, From trees to leaves: a comparison of taxonomies, facets and folksonomies.