I totally disagree with this. What the quote means to me, is that the customer's imagination (for lack of a better world) is so limited, that their problems are sandbox by the context of their understanding.

Something that doesn't shit all over their yard might actually be more important than speed, but they wouldn't even begin to think of asking that because it's not a possibility in their world.

What do you want in the next Blackberry? "real touch" and "real browser" were pretty far outside the box when the iPod touch launched..people weren't asking for it because they didn't know they wanted it (or that it was possible).