Dagon made a point about the social importance of guarantees. If a promise is broken, you know you have been cheated. If you are persuaded that there is only a 10% chance of losing your investment and you are unlucky, what do you know?

I doubt that we can over come our biases by focusing on what they are bad for and how they hurt us. We also need to think about what they are good for and why we have them.