The good news is, you don't have to know about the demand and neither do the demanders! As was mentioned a couple times in the "Will there always be more room for web startups" discussion last week (http://news.ycombinator.com/item?id=89055), customers often don't know what they want until they see it or use it. That unknown demand is why the trial and error of the marketplace always tolerates "crazy" ideas. I agree with your comment that you should ask and find out what customers want, but you can definitely succeed if your instinct matches an unexpressed demand (Twitter, Facebook) or if you can envision a product better than customers can express it (Apple)
"customers often don't know what they want until they see it or use it"
Absolutely.
And I want to be the one who gets to know them, understands their pain, asks the right questions, and prototypes. I want to be the one who is told, "Yes! That's what I want!" instead of those who depend on trial and error or instinct.
And sometimes, I just have to get up off my butt and away from my screen to get that done.
