In my post entitled Drinking From an RSS Fire Hose I dealt with some of the issues surrounding the flood of incoming RSS entries within an RSS aggregator raised by Dare's post "Nightcrawler Thoughts: Thums Up, Thumbs Down and Attention.xml".
The Keep It Simple Stupid Solution
Reading through some of the comments on both posts, I realize that for a great majority of users, a very simple system will satisfy their needs. One user mentioned that it'd be nice to be able to have items with specific keywords automatically marked as read. This is great if you're tired of hearing about, say, Paris Hilton. Add the keyword "Paris Hilton" and no longer will you have to endure her name in your aggregator.
A Short Story
I started to get a buttload of comment spam on this blog recently. I thought about using CAPTCHA, Bayesian Spam Filtering, etc... But in the end, I simply added a trigger modified from this one that simply blocks posts with a certain number of link. This resulted in a dramatic decrease in the number of posts about online poker and has been working quite well for me. At some point, I'll probably need to employ more sophisticated tactics, but for the time being, this simple rule works.
Personally, I think the initial solution isn't a filter at all, but the extensibility model prototyped by Torsten.
On top of this, I'd probably build a simple rules engine plug-in similar to Outlook's. For example, you might create a keyword rule associated with one of the following actions: Mark as Read, Flag For Review, Give Priority, etc... As my short story above illustrates (see, there was a point to it), a simple rules engine approach will often give you the 80% of the 80/20 rule.
The goal with this approach is to get something to the users quickly that will elicit feedback on what the pimped out "baysesian/collaborative/neural networked/throw dart at dartboard" filter should do. A collateral benefit is that users will inevitably create their own plug-ins (we hope) and we have the option to take the best ideas and integrate them as a first class feature.
[Listening to: So What'cha Want - Beastie Boys - Check Your Head (3:37)]