I think it's too early for something like this for Adult blogs in general, maybe Adult webmaster resource blogs if affiliate codes could be included.
Mainstream is fine as most feeds are news sources that are "legitimate" or semi legitimate sites and not just other sites vying for your visitor's credit card.
At the moment, there are
very few Adult Sponsors providing feeds promoting their existing/new products/sites with my affiliate link built into the feed.
When that number increases, your site would be a good resource to choose sponsors who had these feeds if they were listed by sponsor rather than just niche.
Until then why would I put a feed on my Adult blog to bleed traffic/pr to, at worst a competitor, or at best a sponsor I probably don't even promote ?
