Really you have to use your judgment...not all car wash machines are the same. I've had some serious scratches happen at a car wash. It was a cheap automatic car wash places that I went to for the sake of saving some money rather than going to the slightly more expensive ones with newer/better equipment, but then again it was an oversized vehicle that pushes the limits of these car washes. Luckily most of the scratches were on the windshield. The Smart car is so small that the thing will probably barely touch it. I guess I'd be more worried about the water pressure on the soft top than scratches...and then there are the hand automated car washes where people wash the car on the track and it only gets suds and rinsed lightly with some dryers at the end...some of these automated/hand wash car wash places do such a great job that plenty of six figure cars come out of them which speaks quite a lot about the quality that can be achieved in a car wash but these places are twice the price as the cheaper places. Smart cars should get a discount at the car wash for being undersized....it'll never happen.
Then again, an entirely new panel set is $900 to $1100 to replace all the panels on your Smart so should something happen you could get a new color scheme.
That's kinda funny about the laser car wash that refused to recognize the Smart car as a real car in the washer...ha!