tedster - 2:43 am on Aug 7, 2010 (gmt 0)
I've been working with one site for about 11 years in a specialty niche. They have a resources directory that gets (and sends out) a whole lot of natural traffic.
On the Google SERPs it sometimes outranks the websites who are listed in it. While many other directories have seen their PageRank turn gray, all these pages still have healthy green bars. So it's good for the visitors and Google likes it. But we would keep the directory even if Google kicked those pages out of the index, because it is a real service to the market and that's why we maintain it.
And yes, all the categories are custom determined. Thanks Hoople, that's a really valuable point.