As someone who has appalling trouble with categories, the whole idea of the semantic web fills me with trepidation. All I can see before me is a life of endless twirling on the head of a pin, trying to figure out which particular angel should hold my next word.
Ask my wife. My wardrobe is a disaster area, I can't decide whether I should organise it by type (tee shirts, buttoned shirts) style (long sleeved or short) season, colour or use (sloppy, casual, OK for going shopping, acceptable for teaching, public speaking gear, applying for jobs, weddings/ funerals etc) Worse, I just get it right, then do a load of washing and forget what the system is, or find that there are too many for the shelf or some other mess evolves.
The excellent Bill Bryson has many fine passages in his "Short History of Nearly Everything" but the pages he spends on taxonomies rings a whole peal of bells with me.