additionally if you're going to be pulling down public data sets there are probably more interesting and useful ways that you can restructure/reorganize that data. There's a lot of useful data out there that is a real mess that I'm sure some niche would actually pay decently to presented in a more usable fashion
I used to work at a firm that paid gobs of cash for just this sort of data. The trick, of course, is that you need to be well versed in the needs of potential clients before you can even think about staking your claim. But if you know what people need, and if you can collect and effectively present it to them, they will pay for it.
More, if you do it right. Take a look at instantdomainsearch.com. It provides a tiny amount of information, all of which is readily available from other sources. It's still quite profitable.
