I think of these like fine grit sand paper. If you use it on the walls and look closely esp if it is a gloss or semi gloss paint, the gloss is removed. One was used on the countertop in the kitchen and took the shine off. Now it attracks dirt worse than before. I personally don't care for them for this reason. They just have to be used carefully is all I guess. They sure work good for taking off huge scratches on the wall but I'd never use them in the car.
my 2 cents...