Adam Curry encouraged RSS feed inventor Dave Winer to add "enclosures" into RSS feeds so that these feeds would recognize MP3 files. That's how podcasting and video casting were born. Want to see what a feed looks like? This is our RSS feed. Who knew?
Right, you had a question. Unless an RSS feed is created by federal government employees within the course of their duties (here are some examples), you should presume that the material provided in the feed is protected under copyright law. RSS is simply a method of delivery and just like other delivery systems -- television signals, radio transmissions, and newspaper deliveries -- the medium doesn't affect the copyright status of the message. If all you're pulling from the feed is the headline or blog entry title, that's probably not an issue (for example, we pull blog headers from other blogs in the right column on this page). In addition, many news outlets modify the feeds and provide a paragraph from each item along with a link back to the source (and whether that qualifies as a fair use has not been fully resolved, yet).