I'm searching for an ad-supported site in the Site Affinity report, but I don't see it. Why not?

Not all ad-supported domains will appear in the Site Affinity report. For an ad-supported domain to make its way into our Site Affinity report, two things need to happen:   

1. The site must be ad-supported by one of the ad exchanges that our behavioral data partners have contractual agreements with. Our behavioral data partners may change infrequently (about every 1-2 years) and the sites they see will change frequently – with sites being added and removed often. So, this part tends to be a bit of a moving target. 
2. Next, we need to have seen sufficient traffic from the survey respondents that represent the attributes in your audience visiting those sites while we were fielding one of our NCS waves. Again, this piece can be a bit of a moving target. 

Because of these two constraints, you should not be alarmed at the absence of any particular domain in this report.