Site Search beyond keywords

This is going to be a quick one off, because I'm at work. But I'm putting a little time into our site search app (fixing a bug) and a though occurred to me.

Right now we are breaking the data into keywords, from various fields (title, description, tags, etc) and giving each keyword a weight on a per-object basis.

I had a new thought today. Why not log all the past search queries and explicitly check for the top 10% or so of them in every object? Then we could assign a keyword weight to the entire query and get a perfect match on those searches (instead of breaking the query into keywords and searching for objects that have all of them)

This seems like a reasonable way to make smart, phrase based searches rise to the top

PS - I may be able to get my django-search app into the open source, since I havn't found any really good, simple search apps to date :/