This is a video Hank Haney did for Golf Digest several months ago. It's a breakdown of Dustin Johnson's swing, with specific attention on that dramatically bowed wrist of his. But Haney makes a couple of points in this video that I think everybody should be aware of. Take a look:
The first thing Haney mentions -- and I've never heard this before -- is that more women than men have this as a swing flaw. If you've been watching the instructors on GC lately, you've heard a number of them telling you how this position enables you to hit the ball longer AND straighter. This is true, provided you have a powerful swing. Bear in mind that DJ is 6'4" tall, which gives him a huge swing arc and -- according to PGATOUR.com's clubhead speed stat page -- a 122mph clubhead speed with a driver.
It's possible that you might increase your distance off a tee with this technique but, at least on every other kind of shot, the average golfer is going to have the problem that Haney mentions, which is not getting the ball off the ground.
But the most revealing part of this video by far is the proof that DJ actually flattens his wrist during his downswing, which means he isn't hitting the ball with that extreme wrist position at all! Compare his wrist position at the top of the swing (at around the :45 second mark) with his wrist position as he enters the impact zone (at around the 1:38 mark). There's still a little bow in his wrist -- and there should be, unless he's got too much tension in his grip -- but it's nothing like the top of his swing.
It's interesting to note that, in another article for Golf Digest on how to play a flop shot, DJ says that his bowed wrist makes that shot too hard. He says you don't want to bow your wrist at the top, as he shows in this photo. I know he's still got some bow in it, but look at the clubface just above and to the left of his hands. The toe points STRAIGHT DOWN, which is nearly 90° more open than his normal position.
All of this simply illustrates what we already knew, that DJ is a singular golf talent and a physical freak. And regardless of what you may hear, that extreme bowed wrist position isn't necessarily something you want to duplicate.