Okay, you aren't getting it. The point of this is a secret door opening mechanism, but the way they did it puts the actual room near the surface. By default, you'd suspect a room under the person's house. You'd dig there. What's to keep griefers from just digging under your house? Even if the actual place is far from the opener, if they find the redstone, they can follow it to the door. I know you can use this successfully and in better fashions, but the way they did it is too obvious.