
I think that there's a missing category - "size and color".
Once, my cleaning lady found the apartment in pretty good condition and decided to be productive and organized my bookshelf. She chose to do it base on color and size, so that I came home and found that my shelves looked a bit like a rainbow - within each category (red, green, etc.) she used height as a tie-breaker.
My initial reaction was not happy - ironically I had spent about 4 hours that prior weekend re-organizing my bookshelves along more traditional subject matter/author/etc. ordering.
Well - you wouldn't want to organize a library this way, but I have to admit that for my own personal collection in which I personally know how each book looks, this actually worked pretty well!
Old programmers never die, they just hit account block limit.