That's not even the worst part. The many people who have tried to invent flying cars over are finding out that every single thing that's bad with cars (cost, safety, etc) is made worse when you try to make the thing fly.
For instance, no matter what kind of engine they invent, a flying car will always burn more fuel than a regular car, especially on short trips (you burn a bunch of gas trying to overcome that gravity thing on takeoff).
Even worse, even a minor crash with another flying car could send both vehicles plummeting to the ground while you scream in terror. Imagine the poor guy on the ground, sitting there at a red light, as a flaming five car pile-up is hurdling down towards him from the sky. If you're not scared yet, try to imagine what they're going to charge you in insurance premiums as a result.