RSS is commonly defined as really simple syndication. So, this means that any material contained in a feed is available for syndication, right? Well no, not exactly. It means that the content contained in an RSS feed is in a format that is syndication friendly, if the copyright holder allows for syndication. Offering a feed for syndication does not in fact grant any legal rights to anyone to reuse the feeds content beyond what the Copyright laws grant as Fair Use.
In practice, while your feed might legally be protected, you could literally spend weeks attempting to protect the contents of your feed. Legal gray areas are introduced with Search Engines indexing feeds and RSS Feed Directories including copywritten feeds, in their categorized directories. How do you distinguish between a legitimate search engine, RSS directory and someone simply reproducing the contents of a feed for personal gain? Legally how can you defend against one and not the other?