There is a good high-level overview article by Emre Sokullu and Richard MacManus from Read/Write Web on Personalized News.
From the article:
"Personalized Content is one of the two most popular approaches in next generation news sites - the other is Power of Masses, which we will cover in a future post ... First a brief technical explanation: the Personalized Content approach uses a very similar technique to spam detection software. The idea is that everyone has their own pattern of reading. To recognize your pattern, Personalized Content services omit stopwords and extract keywords from the news you read - then use Bayesian Statistical analysis to predict what kind of news you will like or dislike in future..."
And the article concludes:
"...Our guess is that personalized content will become a more popular paradigm in about 1 to 2 years, provided of course that the technical challenges can be overcome. Which is by no means certain, since a lot of smart developers think that personalized content is a huge challenge.
Personalized news has a couple of main attractions. Theoretically, if your news is personalized then it's not as vulnerable to gaming as the power of masses approach. Plus people are getting busier everyday, so personalized news has a strong appeal as a potential solution for information overload.
We're not sure who will end up being the key player in this space - maybe a giant like Google, maybe an existing startup like reddit, or maybe a whole new startup. But one thing we're sure of: the current personalized news services still need more work and the technical issues around personalizing content are far from solved."
The article covers: Reddit, Spotback, SearchFox (now Yahoo!), Feeds2.0, LeapTag and Findory.
Go read it here.