“Basically, reverse brainstorming is a technique that builds on our natural ability to more easily see problems than solutions. Instead of asking a group to brainstorm ideas that would work, the group brainstorms all the ways that it would not work. It is used probably because we are good at criticizing things then appreciating them.
This method can be used simply to provide a different perspective on a particular problem. It is also useful when maybe you have a team with low morale. Reverse brainstorming can sometimes brings smiles to a group that has struggled with new ideas to old and difficult problems. You can use this method as a complement to other ideation methods.

you can read more about it here:
https://dux.typepad.com/dux/2011/01/this-is-the-fourth-in-a-series-of-100-short-articles-about-ux-design-and-evaluation-methods-todays-method-is-called-rever.html“