[fletch]

To me the statements he makes seem OK ish. He is trying to say that for a given size of subject (i.e. the picture you want to take) it doesn't matter what the focal lenght is the DoF will always be the same. I.e. as DoF is a funtion of focal lenght and distance from subject they must be inversley proportional. You can increase one and decrease the other and still get the same answer out of the equation.

In your expample when you zoom in the P&S the DoF gets narrower but the subject also gets larger in frame so although you are altering the DoF you are also altering the picture you are taking which could be looked at as another variable.

Both have limitations in the real world though. You can't always zoom in if the scene you want to capture is wide. For his example; the subject size in frame is not what makes a picture, it is the subject size and the field of view and this changes at different focal lenghts. All of this doesn't really change anything. If you want to get a blured background you still do the same things...

Get close to your subject
Zoom in
Make sure the subject is as far away from the background as possible
Use a large aperture (small f/numbers) if your camera can control this.