Things that fly are really, really dangerous, and the benefits really need to be worth the risks. I don't think a Taco is worth the risk that one of these things goes out of control over the freeway and causes a 100-car pileup. The idea of cheap and plentiful multi copters would make this sort of event inevitable.
Of course there may be a much simpler problem: hungry seagulls.
The article suggests a "modest" speed of 40mph for the quadrocopter, which seems pretty fast to me. Let's call it 30mph. Our car on the freeway is doing say 60mph. Presuming they're travelling in opposite directions, that's 5lbs travelling at 100mph.
So what you're saying is that if I fire a MacBook Pro at car at 100mph then nothing will happen. Unlikely...
And one of these smacking a pedestrian in the head at 40mph isn't going to be much better.
Depending on the design of the frame. Some are made of plastic and break apart really easy on impact. None of them, even the the aluminum frames, are even close to as dense as a MacBook.
Of course there may be a much simpler problem: hungry seagulls.