Chapter 4 Curiosities

If fraud is bad because it hides information and causes a consumer to make a transaction he otherwise would not have made, why is deceptive advertising different? Many times infomercials misleadingly portray a product to get consumers to buy it (say a weight-loss program). The consumers buy the program, yet it does nothing for them. How is this scenario different from a scam? A similar scenario could be an ad for McDonalds. You buy a Big Mac because the picture made it look better than a Whopper, but the product served to you is small, cold, and soggy. You would have liked the Whopper better, so didn't the advertisement lead to economic inefficiency?