I will put stickers on to things. The stickers can be easily removed without marking or damaging anything.
Perhaps you're are familiar with the development of post it notes by using glue that didn't stick very well. The 3 M employee's wife used them to mark hymnals.
The previous poster is using bumper sticker stock.
That is hardly a post-it note. Far different in trying to remove material designed to stay on a car bumper for years.