Reactance deals with the rebellious side of certain consumers who possess an "ironic" hipster attitude. These consumers often shut down and run the opposite way when there is too much outside pressure to buy a product. As cool as it is to do what your reference groups are doing or wearing, some people like to stay out of the mold, rejecting what is popular at the time being (which hipsters do, but then form their own culture, making them ironic).
There are times when I become part of the crowd and copy others around me, and other instances where I exhibit the reactance attitude. One example is with a product called Toms Shoes. Toms fans, please don't get upset. In my opinion, Toms shoes have gone from a noble cause to a slightly corrupted enterprise. There are so many models to chose from now, and they seem to be the most trendy thing you can possibly get. I could buy the shoes because I have friends that wear them, because they're hip, and because they help poor children overseas, but I won't. I feel like I would buy the shoes for the wrong reasons, so I'll never make the purchase.
Marketers must use caution in making their product appear to be the ultimate and only choice for consumers who jump to reactance. If I was the CEO of Toms Shoes, I would continue to stress the benefit to children over the new stylings and new product lines. If Toms Shoes starts making a ton of new products, they will lose consumers such as myself who see the company as somewhat of a facade.