^^^ That sounds like an interesting experience. I had one of those and I was surprised that damn thing did not fall apart on the highway not to mention rolling it. That's good that neither you nor your wife were injured in what sounds like an awful accident.
http://www.youtube.com/watch?v=mT5CvMzgtv8I find this video to be pretty wild. Good old Newton and his laws prevail in this video. From the overhead view you can actually see the C-class transferring it's kinetic energy to the Smart. Although the car received a poor rating the car lacks the weight and size to absorb the energy of an impact the end result is the car takes flight. In a real world collision more damage would come to the Smart after it's little flight as most offset front end collisions do not happen in open warehouses.
This brings up an interesting dilemma that I am sure the engineers of these mirco-machines have faced for as long as these cars have been made. If the wheelbase of the vehicle is <80" and gvwr of <2,000lbs where is the energy going to go when the vehicle is struck in any direction for that matter. With no area for structural support and energy absorbing members that underpin larger vehicles it makes designing safety into these micro cars a challenge. Using lightweight and strong components like carbon fiber would price these cars straight out of the market.
On the same topic of the practicality of these types of small cars, there was an article I read recently about the repair cost associated with 5mph frontal collisions. Not surprisingly the Mini Cooper was one of the most expensive to repair from a slow collision. If you have ever had the "pleasure" of trying to repair one of these you will notice that the engine itself it situated less than 10" from the grill. The headlights are so low and mounted in such a place that almost any collision will destroy them. If the car is equipped with the bi-xenon lights and a turbo the cost of a 5 mph impact with the rear of a truck could easily cause 10 grand in damage.
I really think the size of the Cube would be an asset in this type on collision. It is slightly larger. Although the body components are not extremely cheap the only model specific components should be the sheetmetal and other exterior body parts. That usually make collision repairs easier.