Interesting read.
My current hammer that makes every problem look like a nail is Bayesian filtering (most famously used for spam filtering). The implementations I'm looking at statistically decide whether an email or post falls into the category of "spam" or "not spam". But it takes someone to train the filter by submitting examples of each and correcting it when it's wrong. I've been thinking of different uses for it like "allowed poster" versus "poster non grata" and have wondered if it can identify hot button (for some people) posts like "offensive language" vs. "family language" or "attack" vs "not attack".
I wonder if it could be trained for "my interests" versus "not my interests" to obtain a result like what is described in the article. But to have this customized for each reader there would have to be a distinct statistical database for every reader. Also everyone would have to train their own filters. That sounds like a lot of trouble both server-side and for most readers.
Something I've thought about is to have multiple filters, but grouped instead of individualized. Suppose a poster here whose interest is in individual stock picking trains a filter for his interests and other users can use his filter if they share the same interests. Another user is interested in funds-of-funds and discussion of comparison, and others with similar interests. So in effect you're borrowing someone else's tunnel vision. These examples are much more narrow than I expect in reality, though, and such narrowness is better handled through traditional categorization, anyway.
Incidentally, I don't have the same powers at Andy's servers that I did at dory36's server (for several good reasons for both Andy and me), and I don't expect to be tweaking the site features here like I did in 2005 and 2006. (No more
Days of Jennifer 
) I'm just a simple moderator now, and a pretty lazy one at that.
I have my own sites, and these are ideas I've been kicking around implementing for them. My sites aren't particularly interesting at the moment, but I've recently started toying with them again. At the moment I think I've decided to ditch pre-built software and scratch-build the software myself as it's becoming troublesome to customize pre-built software the way I want while still keeping up with software updates that break my customizations.