why are there so many links to amazon.com and ebay.com when I type those search terms in? It looks as if you give more consideration to the more popular sites.
Questions like this have come up before, but I don't believe we have ever given the most obvious answer. The correlation between our number of links and popularity of the site is often looked at two ways:
1. The site is popular, so we must favor popular sites.
2. We favored the site, and that's why it's popular (perceived boost from dmoz.org listings).
In fact, though, neither of these things are true in most cases. Unique and useful content is the true correlation between the two.
The sites are full of unique content on several subjects, and they are a useful resource in many categories, improving the amount of unique links within those categories enough to justify deeplinking.
and
The sites are full of unique content on several subjects, and they are a useful resource to many people no matter what subject they are interested in, therefore people are happy with them and they become popular.
ODP editors are hard to please. We see a lot more of the Internet than most people, so we see the best and worst of the resources out there. There's a lot to choose from when adding a link to a category, and there's not enough time to link everything, so the sites at the "best" end of that spectrum are more likely to be listed, and deeplinked.
I'm never happier than when I find a great site that can be deeplinked. That means a lot of useful links for the review time of one. But the more great sites there are, the higher that bar gets.
So it all comes down to our mantra "unique content", in the end, which is why readers of this forum see it so often.