I know, it is hard to wrap your head around the concept! You want to think that the infant is much more delicate so should be more protected by being in the middle. But in reality, rear facing is just so much safer--even in side impact collisions. Here is a good quote:
"The most common type of crash is the frontal crash. In a frontal crash, the entire back of a rear-facing carseat absorbs crash forces, protecting the child's head, neck, and spine. In the less common, but more injurious side impact crash, the rear-facing carseat again protects the head, neck and back. Since there's almost always an element of forward motion in a side impact—such as when a vehicle is going straight through an intersection when it's struck in the side by a red-light runner—a rear-facing seat does a better job of keeping a child's head contained within the safety of the seat."
---http://www.carseatsite.com/rf.htm
Remember that the head not being contained in the car seat is bad even if it doesn't hit anything. It stretches out the spinal cord too far. You have to make up for the danger of forward facing by putting them in the middle.