Topic Aggregator?

The words "Web Neighborhood" in one of Jason Kottke’s posts got me thinking. David Weinberger posted the other day an apology to his friends because he was "unable to read all of their posts". I thought this was strange because he obviously would like to keep on top of everything his friends (in his "Web neighborhood") talk about but he can’t because he doesn’t have time to read all of their sites or RSS feeds. Yet I’m sure he would love to hear what they are talking about, especially if it relates to something he is talking about on his site.

So it dawned on me, why hasn’t anyone created a news aggregator that collates and groups news feeds based upon topics in the newsfeeds (I’m assuming determined by grabbing the keywords from the title or tags from the post or maybe even by looking at the links the post is pointing at like Technorati does?). For example, if there were a bunch of posts that had the word "Google OS" in them, couldn’t an aggregator gather those all under a similar heading? And even more so shouldn’t the aggregator be able to list these groupings in order from most items grouped to least so that in effect you get a  "most talked about headlines of the day" at the top to "side stories of the day" at the bottom, almost like you get in a newspaper? I mean you could go farther from there even. If you had a lot of items under one grouping, couldn’t the aggregator grab the PageRank of the site for each post within that group and list them from highest to lowest, so theoretically you are seeing the best site for the topic listed first while the others are listed below (which of course may not always be the case and maybe you could sort the list in other different ways)?

What do you think of this? I mean I know aggregators can do this do somewhat right now in that you can put in your own tags to search for specific things from your feeds but why not let the feeds sort themselves out instead of having to manually enter and look for specific topic keywords? I mean wouldn’t it solves "David’s Dilemma" because then he could just look at the topics / headlines of the day in his RSS news/topic/tag aggregator and easily see if any of his friends in his "Web neighborhood" are talking about the same thing he is? Or is there a news aggregator that does this already that I’m not aware of?

Actually taking this to the next level would be actually embedding this topic feed list below a post on your own site. So if you were talking about "Web OS" then below your post would be a "Related Feeds" list of all the other people on your feed list talking about "Web OS" as well. That way as soon as you finished adding your post, it would immediately show who else was talking about the same topic as you in your "Web Neighborhood"!