Web Directory:How To Evaluate the Quality of a Directory

Depite the recent Microsoft bid for acquiring of Yahoo. Yahoo has been a big sticky site with massive amount of traffic. And Yahoo still maintains a good directory, which is among the top directories in the world.
I remember last time I compare the traffic quality of Ebay and Google, which lead to their different strategy in their recent efforts. For the marketers, this is very important.
In fact, the quality of traffic from directories are as good as, if not better than, that of search engines.
How to evaluate the quality of a directory ?
We can evaluate the quality of a directory from the following four aspects:
Type: Shows whether a service is primarily a directory (D) or a search engine (SE).
Editors: Shows how many people are involved in producing the listings. More is not necessarily better, as some services claim that technology helps them do more. However, a large number of editors can be a good sign that a quality directory is being built and keeping up with the growth of the web.
Links: Shows how many unique URLs exist in the directory, usually as reported by each directory or drawn on recent interviews I've conducted. However, since some URLs may appear in more than one category, this method may produce an overcount.
Categories: Shows how many categories each directory has.
So you can guess, the top three directories are:
Open Directory
LookSmart
Yahoo

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