I think jonpaul is exactly right with his response to the famous Ford quote. Perhaps the customer's imagination is limited, but they know the pain points well. If you're listening carefully, you could figure out the solution. Unfortunately, too many companies use this quote as an excuse to think they're smarter than the customer and develop in a vacuum.

RIM did this. I was a Blackberry to iPhone convert, and I bet a company that was willing to listen to me could eventually figure it out. I would have asked for a browser that actually worked, a larger screen, and thin enough to fit in my pocket (rather than the ridiculous belt clip I had to wear). I had no idea we were capable of the iPhone when it came out, but sounds like my checklist doesn't it?