I may have spoken a bit too fast in my pessimism regarding a script/agent that periodically grabs my subs, picks out the ones "kept as new", marks them as read, and then does something interesting with them. Looking at the Bloglines API namespace it turns out you get a marker for items kept as new. HTTP traffic snooping with Firefox reveals it's a pretty simple request to toggle the mark.
I'm sure there are some caveats, but it seems like an end of the day info hoover a.k.a. knowledge aggregator could be built.