As humans, with a bounded rationality and incomplete view of the world, our communication and decision making ability is limited. Someone take a shot at the concepts of anchoring and group think.
Here are a couple of question that will hopefully stretch your thinking. First - we have attached a probability and impact to a WBS deliverable. Let's say a medium P-I. Could that ever change? Yes or no won't get it. I will need a specific example. Second - let's say that a risk has a combined P-I score in the low range - but the impact is potentially huge. How would you handle it.