Hi Ben,
Isn't what you're talking about a "recommender system"?
This category of applications holds great promise for asynchronous social collaboration about the sorts of things you're talking about.
I've had the opportunity to hear Joseph Konstan of the University of Minnesota & CHI talk about his adventures in this market segment, but I haven't yet read his book, "Word of Mouse."
There's a lot of programming, yes, and there also needs to be a substantial amount of data, yours and others'.