BrainBoost
is a search engine that analyse the text on a page to try to extract the text that answers a natural language question.
I played with this idea 5-6 years ago, but shelved it partly because I don't know enough about natural language processing, and partly because there's a huge problem:
How to determine whether an "answer" is reliable. When you present just an extracted answer as opposed to a full page, you make it significantly harder for the user to determine the reliability of the source.
You also face the problem of how to determine which of mutually conflicting answers are right (and contrary Google's PageRank, you can't determine reliability based on popularity)
Despite that, though BrainBoost is interesting to play with - it's always fun to play with various alternative search engine technologies and see what progress they make.