Too good to be true?

So fenris_lorsrai linked to this project: Solar Roadways. It appears to be AWESOME, the idea of powering America with its highways and parking lots.

However, despite the 8 or so years of research (including government sponsorship), I'm getting major "too good to be true" vibes.

Outside of the general "No one will ever pay for this because there's too many people in Congress who don't want to spend that kind of money," can anyone come up with the various reasons this WON'T work?

Because this is basically what we're getting instead of flying cars, and in all honesty, I'm pretty damn cool with the concept.

(Flying cars would be an utter disaster anyway, as cool as they would look.)