To-date, newspapers have only offered partial feeds primarily because there isn’t nearly as much money to be made in RSS advertising as there is in selling more conventional banner, text, and overlay ads on websites. With a partial feed that only offers a headline and brief summary, the thinking is that people will click thru to the website to read the article, and in turn, load those ads.
The problem with this model is that very few people subscribe to partial feeds, because they offer little value. The Guardian is trying to turn this model upside down, and I think it could be successful, both as a user that wants to consume content in an RSS reader, and from a business perspective for the newspaper.
First and foremost, The Guardian instantly gains an advantage on every other newspaper in the world, because their feeds are now way more useful than those of its competitors. And while RSS may still be fairly niche, The Guardian also positions itself to take advantage of the viralness that is now built into many RSS readers. For example, in Google Reader, when you “share” an item, it is broadcast to your Google contacts, on Friendfeed, and on dozens of other Web aggregators.
Most RSS readers also include the more mainstream concept of simply emailing a story to a friend – something one isn’t likely to do from within the reader when there is only a headline and short summary. While all of that sharing might not translate into immediate revenue for The Guardian, it does give their stories and brand greater exposure in a market that is currently being completely dominated by alternative sources like blogs, most of which offer full-text feeds.