I'm sort-of trying to solve this with a recommender system approach.[1] Search isn't my primary objective; I'm mainly focusing on the case where you want to be made aware of relevant information on an ongoing basis but you aren't necessarily looking for something specific.
But that involves building up a ratings database of lots of different URLs. If it becomes really popular, I'd like to experiment with search. It could start with a "normal" search algorithm but then adjust the results based on rating data. E.g. "the top result for this query is X, but people with similar rating data to you always down vote that link, so we'll move that result down".
I've heard people complain about how Google gives you personalized search results sometimes, but I'm not sure if the approach is actually bad. Perhaps it could work if it was focused on from the start instead of bolted on.