The Cognitive Cost of Classification:
"The mental effort required to consistently assign keywords outweighs the benefits for most frontline contributors to content, document, and knowledge management systems. Contrary to KM World’s recent facets summary, faceted classification can actually compound the problem. Facets are oversold in situations where info-civilians have to classify content that they have created themselves. Expecting facets to solve the metacrap problem is naive."
And: "faceted classfications multiply the number of decisions required to classify a given document."
Um, facets aren't meant to make classifying easier, they're meant to make finding easier. And I can think of a few ways of how they'd make classifying easier, too - classifying something in 5 facets is not necessarily more cognitively complex than classifying it one place in a taxonomy. I have to disagree with Jess here.