I'm pretty new to the game (started this month), but from what I've seen, breaking your content up into specific niches seems to help. If someone has a specific niche in mind for their exclusive content, their additional feeds should compliment that content. If their site is all latin boys, all the time, you'd do better by having a feed available with just latinos in the scenes.

I work as a sales monkey for Topbucks, and we offer bonus content from other providers (yup, we sell feeds and we buy feeds...hurray for information-age capitalism!) and that content is almost always geared to the niche our site was already targeting. I know this is an extreme example, but you don't want to have a twink site with bonus MILF content, it just doesn't make sense not to have the bonus feed match up with the main content.

Also, that bonus is a key idea. Like you guys said, everyone is all about exclusive content, so feeds would be icing on the cake, especially if the site is small time and has limited exclusive content they need to flesh out, as it were.

Sorry if I'm rambling, but cold medicine has made me loopy:prescription: