Privacy Guard: You Don't Need to Scan My Drivers License

Technically true, but unlikely to be a real issue unless you're presenting the ID to a police officer or other official that legally requires it. If it's a sticker, then it's easy to remove it prior to presenting the ID. In my state, only permanent alterations are illegal. Putting a sticker on your driver's license is allowed, but officials can remove it (The ID is state property, after all, not yours.)

The best solution is to tell businesses that want to scan your ID to go take a hike and take your business elsewhere. But if that's not a realistic option, I'd have no qualms about using a sticker like this temporarily. Attach it before entering the establishment, remove it when you leave.

That said, many establishments that scan IDs aren't scanning just the bar code. They're taking a photo of the entirety of the front and back of the card. These stickers are less effective at protecting against that.