Most directories have the same or similar category structure, often DMOZ or Yahoo inspired. The problem is, it's quite bland, and besides, the category structure isn't even very good. Does every directory really need an "Arts and humanities" section? "artificial life"? I don't mean to pick on these two in particular in fact I could choose many different cateogories. I give these just as examples, but also because most internet surfers aren't interested in either of them. Besides that, if you want arts and humanities, you'd go to www.aldaily.com or something like that; you wouldn't go to a general directory. How hard is it to change the names to your own personalized category structure? Not hard at all. All it takes is a little bit of thinking and imagination and planning. Directory owners, please. Show some imagination. Break the mold! Enough of the bland, same-same-same category structures. Go your own way!
Its good advice - I have designed some bespoke directory software myself and I always install it with no categories then I go through and add only the categories I feel are appropriate and useful. Yes it takes a bit of time but its worth it in the long run. I always try and avoid adding categories aswell until the existing categories are filling up.