This, for example, just arrived:
Imagine walking down the street. It's 5pm on a sunny Friday afternoon. You're hungry after a long day at the office. You smell pizza, but can't quite figure out where it's coming from. As if by magic, your phone vibrates. Why? The source of your olfactory torment is a mere two blocks away. Your phone prompts you with "40% off a slice of pizza if you come in now."
Does that setup seem at all plausible? Would this ever apply to you?
I get one of these a day, I bet. I don't know a single person who has or would sign up for a service like this.