OK, let's complicate the situation another step. What if you are designing a product or service and have a choice to make. There is one option that would be more profitable, but would be worse for the customer. They would think it was better, sales would be better, and they would never know it. Do you do it? Is it worse if the customer is a child?
I saw on Facebook so many times yesterday that I am sure everyone has already seen the article about Spongebob Squarepants. They design the show to shift between scenes really fast. This hampers a child's development of executive processing such as attention, working memory, problem solving and delay of gratification. These all help kids get ahead in school and in life. But kids love it because it captures their attention fully. So if you were Nickelodeon, what would you do about this?
A saw a TED talk abstract (that I think I misinterpreted at first, but makes a better example) with a similar case. There is an iPad app for kids that tells stories. But if the reader doesn't like the way the story is going, they just shake the iPad and it goes in a different direction (I remember books like this when I was a kid, but not as visceral a method of changing the plot). What does this teach? But kids love it.
What would you do if faced with this kind of decision? As a designer? As a parent consumer?