Very clear pros and cons of folksonomies versus more traditional classification systems. Looks at when and for what each kind of classification is most useful.

"Philosophical relativism appears to be the underlying philosophy behind folksonomies. Because of those underpinnings, it is possible to jettison the limitations of a traditional classification statement such as "A is not B". In a folksonomy system, "A is relative to B", because each item's index terms will depend on the individual user and the tags he or she decides to use. A philosophy of relativism allows folksonomy to draw on many users with various perceptions to classify a document instead of relying on one individual cataloger to set the index terms for that item. Thus, classification terms become relative to each user."

Another one of those articles that describes the whens and why's of traditionaly classification schemes versus folksonomies and tagging systems.