Getting the message out, but perhaps not very effectively

Adhesive advertisement for ADT Security, Cambie Street, Vancouver, BC 

Whenever a retail premises is vacant I see these stickers on the front door. As you might guess, the white rectangle is a business card and the card is removable once the sticker has been removed from the door.

I have no idea if these are at all effective, but I suspect that they are not. I'm the only person that I've ever seen pay the slightest attention to them. They remain on the doors of vacant shops for weeks unnoticed and unloved.