I just thought of this today...
When using RSS some sites don't feed the headlines, summary and date information. They feed the whole page HTML content in the summary field, so when an user clicks on the headline in the reader, the whole page comes instead of just a summary.
In my case I only give the summary, because I want people to visit the live site.
How does it impact traffic to a website? I tend to believe it brings more visitors, because other webmasters rely on these feeds to find "news" to post, and since only link, summary and headline is available readers have to visit the real thing to find out more.
How does it impact AdSense? I've noticed that some content in RSS feeds include AdSense code in the summary, and it shows up in some RSS Feedreaders (line SharpReader), because these just use Internet Explorer to show the content. It's not technically "frames", so would it be allowed?