California Dusters are real bad for paint.
As a blanket statement I disagree. It dependings on the use. While dragging something across your paint isn't always the best idea, I've found the use of a California Duster, lightly, on a regularly waxed car causes absolutely no damage or swirling. Of course, the car must only be dusty and not dirty, but it works. Also the greener/yellower the dust the more pollen that makes up said dust which is more abrasive. I definitely wouldn't recommend the CD on a car covered in large amounts of pollen.