The problem is the very personalized nature of the feed. My understanding of how most RSS aggregators work is that a central "authority" identifies and adds feeds to a particular interface. Thus I can't add my "saved search on foo" so that only I can see it. I can imagine that there's an existence proof that some interface out there allows the user to directly add their own feeds, but what is desired is that a user of my search engine could add their "saved search on foo" (and *not* their "saved search on bar") to their favorite aggregator.
Am I right in my understanding of this problem? I have to admit to a merely theoretical understanding of RSS with the belief that I probably use it more often than I know (except for early experiments with my.netscape).
BTW, I'm not the only person to want saved searches available ia RSS: "In the future, I hope to retrieve saved searches from the popular news engines like World News via RSS feeds and postings to listservs to which I subscribe. " See http://www.llrx.com/features/rssforlibr