It doesn't look bad for a start. Here are a couple of thoughts (some already mentioned above):
You're using your shoulders much and you're not using your hips at all in the stroke. There's tons of free, effortless power there. You want to rotate your hips into the shot, which then pulls around the shoulders, which then drives the arms and finally the racquet through the contact zone. You're doing it almost all with your arms a little shoulder right now.
Your set-up and swing into the ball look really nice. Just pausing the youtube video I'd say you look really good right until right before contact. You're getting the racquet back, shoulders turned, neutral stance with good weighting. Just at the point when your hips should start rotating into the ball instead your arms start to come forward.
Here's a couple of guys with decent-ish backhands.
http://www.youtube.com/watch?v=uJpmtCm70Vc&feature=relmfu
http://www.youtube.com/watch?v=-k40zmz1uvA&feature=related
http://www.youtube.com/watch?v=ql5xVpACt1Y
Watch their hips and shoulders as they hit. And note that these are just warm ups. Neither guy is trying to murder the ball, they're just using good, efficient form.
For what it's worth, you get more hip rotation and hence free power with your forehand. I think you could get more, but the point is that on your forehand you probably have a feeling of your shoulders and arms being pulled around a bit as you rotate into the shot. You want that feeling on your backhand too.