While Divisdero is a pretty good operation for getting a car wash, they have damaged outside mirrors on two occasions that I'm aware of. Once to my car and once to a friends car. The damage wasn't immediately noticable, so in both cases we didn't notice the damage until later, after we left.
Of course, they denied everything and there wasn't really any recourse. However, you'll notice that there is now someone that video tapes all the cars as they come in (they didn't always have this). They walk around each car with a video camera. I doubt they would have someone doing this unless they were frequently damaging cars.
So, make sure you fully inspect the outside of your car before you leave. Especially anything that sticks out, like side mirrors.