Rule of thumb

If you are opting into a link directory and that directory uses an automated process then consider it a bad investment and don't waste your time.

If the directory you are paying for inclusion uses a manual review system like Joe Ant, then count it a good investment and worth your while.

I am not saying that manual reviews are beyond corruption (DMOZ), what I am saying is that the search engines are less likely to discount the editorial process of a human edited directory.

A similar thought should be applied to reciprocated link trading...

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You can lead a blonde to reason but you can't make her think!