Security
I've been following the Terrafugia loosely for a while. It not something I'd ever be in the market for (too expensive, not aerobatic enough, and needs about 200% more power :-) but I have to admire the guys trying to solve the vast number of engineering problems involved in building a flying car. Sorry, "roadable aircraft".
Something's been bugging me, though. The whole pitch seems to be that you drive it to the nearest airport and take off from the runway. Nice in theory but, in the US at least, have you tried "just" driving into an airport lately? I live in the San Francisco Bay Area and the three nearest GA airports (all within 25 miles) are Oakland, Hayward and Livermore. Oakland is a fortress and the other two are almost as tightly locked down. It's not like there's a security guard at the gate who can check your ID and let you in, either - if you don't have a badge/smart card you're not getting through the gate. Even more remote, non-towered airports are getting harder and harder to get a vehicle into.
I haven't seen any evidence that this problem has been considered or solved yet, at least in the US. Any ideas?