Whoa. Strangely similar to an idea I had recently too. Yes, ideas are cheap but the plethora of public domain information is immense: housing, census, financial and other is just begging to be wrapped in an intuitive interface that welcomes research and exploring.
edit: informal project anyone?
Absolutely; the data is there. Businesses and governments are willing to pay for a better way to dissect it too. And people who create these new companies will be helping governments become more transparent so that we the people can take back power that has been systematically stolen (or just lazily handed over) throughout the last several decades.
The "public" agencies aren't going to take scraping "their" data lightly, especially if they have a data contract with someone like Dialog.
Congressional offices aren't likely to pay. Govt agencies might.