...Rational economists make recommendations regarding the ideal way to design health insurance, retirement funds, and operating principles for financial institutions. This is, of course, the source of the basic belief in the wisdom of deregulation: if people always make the right decisions, and if the “invisible hand” and market forces always lead to efficiency, shouldn’t we just let go of any regulations and allow the financial markets to operate at their full potential?
On the other hand, scientists in fields ranging from chemistry to physics to psychology are trained to be suspicious of “established facts.” In these fields, assumptions and theories are tested empirically and repeatedly. In testing them, scientists have learned over and over that many ideas accepted as true can end up being wrong; this is the natural progression of science. Accordingly, nearly all scientists have a stronger belief in data than in their own theories. If empirical observation is incompatible with a model, the model must be trashed or amended, even if it is conceptually beautiful, logically appealing, or mathematically convenient.
Unfortunately, such healthy scientific skepticism and empiricism have not yet taken hold in rational economics, where initial assumptions about human nature have solidified into dogma. Blind faith in human rationality and the forces of the market would not be so bad if they were limited to a few university professors and the students taking their classes. The real problem, however, is that economists have been very successful in convincing the world, including politicians, businesspeople, and everyday Joes not only that economics has something important to say about how the world around us functions (which it does), but that economics is a sufficient explanation of everything around us (which it is not). In essence, the economic dogma is that once we take rational economics into account, nothing else is needed.
I believe that relying too heavily on our capacity for rationality when we design our policies and institutions, coupled with a belief in the completeness of economics, can lead us to expose ourselves to substantial risks.
Here’s one way of thinking about this. Imagine that you’re in charge of designing highways, and you plan them under the assumption that all people drive perfectly. What would such rational road designs look like? Certainly, there would be no paved margins on the side of the road. Why would we lay concrete and asphalt on a part of the road where no one is supposed to drive on? Second, we would not have cut lines on the side of the road that make a brrrrrr sound when you drive over them, because all people are expected to drive perfectly straight down the middle of the lane. We would also make the width of the lanes much closer to the width of the car, eliminate all speed limits, and fill traffic lanes to 100 percent of their capacity. There is no question that this would be a more rational way to build roads, but is this a system that you would like to drive in? Of course not.
When it comes to designing things in our physical world, we all understand how flawed we are and design the physical world around us accordingly...
And
2.) Even if consumers make mistakes from time to time, wouldn’t the market fix these?
I always found the appeal to the market gods a bit odd. Why would the market fix mistakes instead of aggravating them? When the Chicago economists sometimes (reluctantly) admits that people make mistakes, they claim that people make different types of mistakes that will eventually cancel each other out in the market. Behavioral economics argues that, instead, people will often make the same mistake, and the individual mistakes can aggregate in the market...
http://danariely.com/tag/behavioral-economics-2/ 
