Steve Pepper disagrees, and argues that ideally the PSD (Published Subject Descriptor) should incude the minimum of information needed to unambiguously identify the subject.
Robert Engels then enters the discussion and argues from the RDF point of view.
My view is that I would currently use Wikipedia, because on some subjects it's the best source I got. I agree with Steve Pepper, but imagine that it could be useful in some contexts to be a bit fuzzy on purpose. A widely defined and a bit fuzzy subject might be exactly want we want, to be able to "start a conversation".