Sean Foley made a reference to this in a Revolution Golf video. I guy by the name of James Leitz has invented this crazy tool to demonstrate the relationship of the swing plane to the swing path and the club angle. I always thought you wanted your divots to point to your target line, but this model shows why and when that is not true especially when you are hitting down on the ball (i.e. low point of your swing is ahead of the ball position) and the club shaft is leaning forward at ball contact (which is something the Tour Striker training tool is making me better at). Here's the video:
And here's the link to James' web site that shows the D-Plane model in greater detail. Sheesh - my head is spinning.