Some months ago, I read The Looming Tower which I see has made the New York Times list of best books of 2006.
It includes stories of worldviews shaped by various forms of poverty and strict doctrines being deliberately distorted by others for political purposes and reminded me of September 12 2001 when, in an article in The Times, I first read the word Wahhabi. The writer commented that it was a word that we should all be looking out for in the future. In the west, I imagine a very small amount of people were aware of it. I now know it, maybe you still don't.
People "know" stuff. I "know" stuff. You "know" stuff. Your potential customer "knows" stuff. It's crucial however that you really know what they know because your interpretation of common knowledge is just that. Your interpretation. Nobody else's.