I don't think the flying car or jetpack is really that crazy of technology. We can easily make quad-copters for personal transport. With enough investment, it could become a commodity good.

But, think about how bad the average driver is. Now realize that they're driving in two dimensions. What happens when you add a third? Terrible, terrible things. That's why we haven't invested in any infrastructure in flying cars, and without that infrastructure, it ain't gonna happen.