Also, the nattering nabob of negativity is important in reminding people that prioritising the thing that probably won't work or is difficult to make work has t

Also, the nattering nabob of negativity is important in reminding people that prioritising the thing that probably won't work or is difficult to make work has the opportunity cost of not prioritising things that will work. Sure, the negative voice might occasionally deter you from finding an incredible solution, but the positive voices about ambitious ideas are always deterring you from focusing on fixing other stuff. I view my lack of success as the "that don't won't work" person in one role as the reason why we had a number of half finished products that didn't work or didn't sell. At least if a team agrees to try something that probably won't work because the rewards are so huge (or the implementation is easy and it's just the results that are questionable) they've thought about the resources needed, and won't either give up at the first hurdle or plough far more into it than it'll ever be worth.