web, Dewey Decimal System, and classification

In the last two-three years a huge amount has been written about tagging and folksonomies, much of it with the bright-eyed enthusiasm of those who haven't seen the present state of affairs in a broader light; but where is the fight-back from the formal classificationists, who hither-to ruled unchallenged in this area? Have such giants as the Library of Congress and the Dewey Decimal System fallen at the first hurdle?

Tagging is the assigning of arbitrary tags to content by amateurs (typically content creators, editors or readers) and folksonomies are systems built from the ground up using these tags. Tags have no formal meanings and there are no constraints placed upon them. Folksonomies are central to systems such as flickr, del.icio.us and the whole web 2.0 approach.

Formal classifications, such as the the Library of Congress and the Dewey Decimal System are rigorous systems in which trained individuals assign subject categories to content. Each category has a description and is long lived—categories don't change even when the words used to describe the topic in popular culture change. Thus the LoC still calls cars automobiles, because that's what they were called when they first entered the system.