I once got hit in the face when I wasn't even playing (was on crutches in the stands...unrelated to dodgeball lol). I was working on class work that I'd missed and didn't see it coming!
Well, the point is that you can't always dodge. If I recall, we would mostly go for head-shots, but more to teh back of the head, so they wouldn't see it coming. We were pretty little when playing this, like 3rd grade, so it wasn't like some rocket of a ball laying kids out flat.