>> What if I want to start a site which actually reviews various affiliate programs (and links to them)? Somewhat like an affiliate directory?
Though issue here <img src="/images/icons/smile.gif" alt="" /> As many other fellow editors said, we do look to unique content and the surfer's experience. It can be argued that a comprehensive directory of affiliate programs might be a usefoul resource for surfers looking for... affiliate programs (not that users aren't already hit with endless spam by the oh-so-innovative affiliate marketers, but this is another issue), but here too if the content is merely a list of (affiliate) links to affiliate programs, such a site won't be considered for inclusion.
A somewhat good test could be the following:
a) take site foo.com
b) strip out all affiliate content (links containing affiliate tags) and call it X
c) strip out all duplicated content (content already found in other sites, either copied/grabbed, syndicated, etc.) and call it Y
d) take what you have left and call it Z
Now look at Z and consider looking both at whether this could be of some value for the surfer and weighting Z against (X + Y)
If Z could still be considered an useful resource for the surfer and still weights more than (X + Y) the site sure could be eligible for a listing.
If Z could still be considered an useful resource for the surfer but its weight is less than (X + Y) the site may or may not be eligible for a listing, depending on the uniqueness and value of Z (and here editorial judgement comes into play).
If Z couldn't still be considered an useful resource for the surfer and its weight is less than (X + Y) the site sure couldn't be eligible for a listing (standard characteristic of the hundreds of affiliate linkfarms, bannerfarms, content-reproducing, claiming-to-be-a-directory, spamcrap we see every day).
Thake all this as a very general rule, since as you can understand any more exact formula will just make no sense. Editorial good judgement (after all, it's what we are here for, reviewing sites) coupled with an understanding and application of the Guidelines, is what makes a human edited directory different, after all.
Also, consider that talking about affiliate content vs useful content, we often see sites submitted which are acceptable, and then add loads of affiliate links (or affiliate tags to the existing, previously non-affiliate links) after inclusion. In one of the forums you visit, someone made a very goot point: "The problem is once you publish a specific policy, someone will find a way around it by the time they finish reading it" <img src="/images/icons/smile.gif" alt="" />