My impression is that if you're not dealing with people trying to game the algorithm then it's all a lot simpler.

As to data sources - with a constrained set of sites the creation of custom adapters should be do-able I'd have thought.

Not that I have any plans. Maybe I should though :)

Edit: come to think of it, it's practically an internet law that stuff you think of already exists. So maybe I should just post an Ask HN for the link to the search engine in question...