I agree with Keith on keeping your back tight; it's a little rounded when lowering the bar.
My main concern is how you're squatting when you receive the bar. It looks like you're hips are coming way too far back and this is causing your torso to fall forward. I know in CrossFit they will teach you to "sit back" and tell you that letting your knees pass your toes is forbidden. Well in weightlifting what you want to do is squat with your hips straight down and if that means your knees are going to pass your toes then so be it.
Keep working on the correct squat technique (hips straight down) and let that transfer over to the clean.