There are some things better done via other routes. For the directory to be useful people drill down through our categories until they reach the one for the keyword they might search on. There they can drill down further by a secondary keyword, until they reach a list of sites that meet what they are looking for. Most of the time we will present them with a list of 10 to 80 sites, each one of them different (we hope). Of course you do get some areas, such as web designers which is still a very fragmented industry of individuals and small companies each offering something different and you get into the tens of thousands, but those are exceptions.
If we were to accept affiliates then across whole expanses of commercial categories we would be offering the surfer not 80 but 8000 sites, but still only 80 variations. Isn't that what Google and other search engines do? Isn't it the reason why for many, search engines are next to useless, why hundreds of millions of whatever your currency is spent on SEO. What editors share and are passionate about with regard to DMOZ is that we do everything about face - SEO means nothing to us, we don't use robots to list everything including your granny's shopping list, we are interested in only the best sites in terms of high quality original content, something everyone can do but few feel the inclination to do, and our decisions are based on value to surfers not how much money has been spent. The end result is a resource of genuine value to the web surfer, who don't have to wade through piles of irrelevant results and duplicates as they would in a search engine.
So affiliate sites - market them through search engines and affiliate exchanges. Sites that are genuinely unique but are partially funded by discrete affiliate advertising are fine by us but not those with affiliation as the concept. One day, I suspect, the likes of Google will work out an effective method of eliminating affiliate sites from their search results and that route will be closed too. It can't come too soon.
