I'm working with a client that has a consumer-based application to provide energy-saving tips. There is a long questionnaire, so the system uses a lot of intelligent defaults based on what utility and third-party information the system has access to, as well as local, regional, and national averages.
So, at first glance, the user fills out a handful of fields and gets energy-saving tips and savings estimates. But, the more fields that they fill out with real information, instead of the defaults, the better the estimates.