I have seen a gas station with no less than 9 big flags in front of it, saying that you get $X off when you check in at Facebook. I guess it might work because

I have seen a gas station with no less than 9 big flags in front of it, saying that you get $X off when you check in at Facebook. I guess it might work because you read the name of a friend in the same sentence as the business. It might work even better with sandwiches, because that's something you can actually recommend. (Gas is all the same.) Source: Taiwan