Has anyone yet developed a bumper sticker (not a big magnetic door sign) that is waterproof and will stand up to a car wash, but that can easily be pealed off without leaving residue? If not, someone on the Form should invent and patent it and make a small fortune.
I don't like to have much in the way of identifying stickers on my vehicles, but when I do use them I put them on the rear windshield so that I can eventually scrape them off with a razor blade and remove left-over adhesive with an emulsifier. Won't put them on a bumper or the vehicle's body just for this reason. For a temporary-use sticker (like this one, or one supporting a political candidate), I'd pay a lot extra if it were something I could easily apply and then just as easily remove six months down the road.
(BTW, I do have some gun cases with stickers on them, so that would be a great place for HB 560 bumper stickers, too. For smaller accessories like round stickers or refrigerator magnets, options like CafePress exist where Charles wouldn't have to buy in bulk in advance; they could be purchased print-on-demand directly from the print provider.)