One thing we have noticed is that sponsor feeds usually do not have any time or date variable in them. What this causes is duplicate feed URL's for the same sponsor site which wordpress will ignore as a duplicate post.
sponsors need to put some date/time variable in their Feed URL's. this will help maximize the ability to use their feeds in promotion of one or more sites.
Here is an example of what i am talking about.
An example of this is the Top Bucks RSS generator. While very flexible and easy to use, it does not put any specific date or time variables in the URL string of the feed, and if, for example, you generate a feed for their site His First Gay Sex, today, and post it in your blog, and then go back and generate a new feed for the same site tomorrow, wordpress sees the rss url as the same feed and the second one will not show up.
Here is an example.. (this is a feed for His First Gay Sex, using a 4 picture layout, black text, medium font)
http://rss.topbucks.com/?revid=xxxxx...feed=staticpic
(this is a feed for His First Gay Sex, using a 2 picture layout, blue text and large font)
http://rss.topbucks.com/?revid=xxxxx...feed=staticpic
You will notice that even though the feeds had different parameters, the URL's are the same. And the second and subsequent feeds for this sponsor and this website from the sponsor will not show up in wordpress because of the url being the same, no matter when the feed was generated or posted to the blog.
Please keep in mind I am in no way slighting Top Bucks as they are very responsive to affiliates needs and have created a great product..just using their feed as an example for this issue.