Back when I got my car new, it had a sticker in the window that left a rather annoying sticky residue. I used a scotch bright pad, abrasive side, to clean it off. I figured, toughened glass, that's not going to scratch right? Later I was horrified to find loads of permanent scratches on the glass where I had cleaned off the glue. Lesson learned.

There's a reason why car sponges don't have an abrasive side. It scratches paintwork.