text: A good reason for this is for advertising. The article states that ads can be modifyed to show things that make you happy and could make you purchase it. If you see a ad you don't like you won't get ads like those anymore, insted it will supply ones that will possibly make you happy, if you still don't like those ads, the process will repeat will you do find a interesting ad. This could lead to higher sales, but also lower sales.