From an article on BoingBoing.net
"This is scientific uncertainty--where the things we know and the things we don't know collide, and we are left to figure out how to use what we have to make decisions anyway. If we want people to understand science, we can't just give them facts to memorize. Scientific literacy isn't about being able to win a game of quiz bowl. It's about understanding how science works, and how science can be used to guide human decision-making. It's about knowing that we don't have all the answers. But it's also about knowing that "we don't have all the answers" isn't the same thing as "we don't know anything." If we pump people full of facts, but don't teach them about uncertainty, then we can't be surprised when they dismiss anything that isn't 100% certain"
Just a note that uncertainty doesn't score well on standardized tests.