Problems with vertical lift vehicles.
Despite nearly 70 years of practical vertical lift vehicles (helicopters primarily, and everything else lumped in, from the flying platform to the Harrier), their current and future uses for mass transportation are highly constrained for two main reasons.
The first is the very high operating cost per passenger-mile (or ton-mile).
The second is lack of infrastructure on the ground. To put it another way, nobody wants a heliport within earshot.
The flying car idea has been around a long, long time. Their are many objections to this latest incarnation. First, the costs will be horrendous. Second, engine-out performance is a big question (multi-engine design is absolutely essential, because the thing can't autorotate). Third, the FAA will have to certify it. Fourth, the noise signature will mobilize community opposition. Fifth, there's no infrastructure for VTOL operation (Do you really think you're going to be allowed to land in a parking lot?). Sixth, this will be an aircraft and will have to fit into the ATC system, with all that that entails. Seventh, it will require a pilot certificate, AND a powered-life one at that, and obtaining one of those, my friend, is sure to be a high-dollar proposition.
I'm sure many more objections are there, but these seven are just off the top of my head.
About the only thing the "flying car" idea is good for is to ensure a month of good sales for the "Popular Gizmo" segment of the magazine industry every couple of years. That's been working for them for about, oh, let's see now, since 1930....