The search engines detect rss feeds and discount or simply ignore them rather than penalize a site because it know the original source of content.
Bob is absolutely right saying what he just said. Search engines won't penalize for duplicate content in case of RSS feeds. RSS feeds are meant for that purpose and they very well know.
Bullshit. Why should they have a special algorithm just to detect RSS feeds? Yeah, they wouldn't. How many times have you seen RSS feeds rank in Google? I have seen them a LOT. What you do is prevent the feed from getting indexed via robots.txt in the first place, done. And there is also no fucking duplicate content penalty. It's a dumbass assumption that Google is too stupid to recognize that a lot of CMSs create pages with essentially the same content and to then assume they PENALIZE those sites for that is beyond moronic.
As the man so eloquently said, there is no 'duplicate content penalty'. There is, however, a 'unique content bonus'.