That's a pretty picture. Editors as category builders.
Most categories are overseen by editors without any proper knowledge of the subject. They are edited from the top, if you will.
Example. One editor has a special knowledge of metal crafts. He works his way up the craft tree, and can now edit any craft from lacemaking to quilting. Can he be a category builder for lacemaking? No, he cannot. He can at best be a "site suggestion processor."
An overwhelming majority of deep categories have no editor at all, and are "processed" by editors that do not have the dedication to build categories.
Specialized categories are thus filled with unrepresentative links for antiquated sites, while new sites take up to 3 years to show up. For the surfer, a better alternative is often a link page within a topical website.
Search engines would be foolish to favor such haphazard material as that which is supplied by dmoz.
Rich offers many suggestions, but I believe that dmoz is forever hopeless as a search engine booster.
I am happy to hear that some people find it useful on days that the search feature works properly.