Recently and quite often, people with no programming background come and say they have this great idea that can be the next big thing and that the idea(s) is worth a fortune by itself. Then as they know I'm a programmer, they ask me if I'm willing to "code it up" for them or find someone willing to do it for next to nothing.

Judging from the enthusiasm, it's like they're drunk on their idea and that that by itself is the most important thing, but they just need a programmer. My response to them, depending on my mood and their general attitude towards what we do, is something along the lines of:
"Having the core of an idea is one thing. Developing it to the point that it becomes a platform that changes the world in which it lives is another, and you're going to be willing to pay proportionately to how big you think your idea is worth."

Have you been approached by these business type entrepreneurs (with no technical/developer's knowledge) with such a proposal and how do you react to them?