PageRank does it.
Here's a critique of MemoOrandum : http://www.roughtype.com/archives/2006/03/the_editor_and.php
Compare my comments on personalized filtering here : http://dannyayers.com/archives/2006/02/15/personalised-filtering/#comments
Maybe Im missing the point, but wouldnt blog personalization be better done on the individuals machine? Ie. what about trying to solve the problem of finding whats relevant to you in the 300 feeds you subscribe to, based on local information available in those feeds. People with patience (or fast connections / machines) can expand that list.
Maybe there are ways that people can also re-export some of the crunching that goes on on their local machine. Eg. if your smart aggregator has ranked all the posts in the 300 feeds it receives by some calculated relevance to you, why shouldnt it be able to export that ranking, and my aggregator can monitor that information and use it as a hint for weighting those posts for me.
DaveWiner putting pieces together : http://scripting.wordpress.com/2006/03/10/river-of-meme-o-randum/