The Community Engine Blog: Newsgator: Taxonomy and Folksonomy is a great post on how RSS reader archives can be categorized. This alludes to using a folksonomy environment as a working space for clues on how to build the taxonomy. That is, build the taxonomy based on a prior user defined system (ie. a folksonomy).
This is Marketing 101, learn what the customer wants and then build it…you can’t go wrong!
In this example, to understand; which items are tagged, how many times an item is tagged, common tag names applied, and who the tagger is…then base your content and taxonomy on this information.
This is KM 101, users organising data into information and then the taxonomer making inferences, and turning this information into knowledge…hence a usable taxonomy!