Hate to burst you clowns bubble but I'll give you a lesson in Statics (
http://en.wikipedia.org/wiki/Statics for most of you, since you probably have no fucking clue what it means) & Mechanics
http://en.wikipedia.org/wiki/Mechanics . The shelf above appears to have the pins about 1" in from the edge. In order for it to tip over, the tip of the foot would have to be just on the edge. The further in the foot is, the less likely it is to tip. If the foot is a few inches in from the edge, there is no way it will tip forward. The heel doesn't have to be over the pin either. It would most likely come crashing straight down from the weight as the pins would give way. However, if you distribute your weight between it and one you have your hand on, reach up and grab something off a higher shelf, you will only be on ift for a split second and your momentum going up will lessen the load on the shelves. If the pin was 4 inches in from the front, it would be a different story.
The palm of the hand in the picture is placed on the very edge, pushing at an angel to best make the shelf tip. Couldn't be any more blatant.