Why have most personalized news startups failed?

There are some really great answers here. But I think one thing that's worth considering: I think for many people, the "discovery" need re: news is filled. While people are busy trying to make sure a "personalized news service" really finds the content consumers care about, consumers aren't necessarily looking for that. They're getting what they need (and for many, way too much of it) through Twitter, RSS readers, and other sources. This has the added benefit of really making sure their news was anchored socially, that the news was something they could discuss with other people. The larger issue now for these folks is, how do I prioritize my content? People have seemed to come up with arbitrary systems now, popular on Twitter is just focusing on the news shared in "real-time," right when I happen to be bored and looking for an answer. But it would be interesting to think about how one might go about "prioritizing" news for individuals, once they've discovered new articles (Marco, where are you with the next-gen "intelligent Instapaper"?).