There are lots of 450's up here in Canada, though not quite as many 451's on the road, surprisingly (well, at least not where I live in rural farmland!) however since the big price slash at the dealerships, there are more of them passing through town ^^
Haven't seen any ForFour's or smart roadsters though.. it's a shame they don't produce the roadsters anymore, that was my first experience of a smart car and they are mega-awesome fantastic
A "cabrio" by the way is a convertible.. seems to be the preferred synonym used by euro car makers