I saw these things everywhere in both London and Paris. They really are tiny, with the models I saw only being around 6ft. in length. They have to be extremely thrifty with the gas, though. Last year, gas was the equivelant of around $5-6 dollars per gallon. Many people there use Diesel because of the better fuel ecomomy. Can you imagine a collision involving a Smart Car and an Expedition or Ram?
That would be my only qualm about these 'ultimate commuter cars.'
Cheers!