Here is an undamaged airframe for comparison.

                                                            

In fact, in general, the rearward Center of Gravity limit represents the aft most CG for which the tail plane is still generating a down force.

The forward Center of Gravity limit represents the point at which the tail is unlikely to reach critical angle of attack before the wing during the landing flare; at full flaps and with a range of power settings.

Let us picture this.   The flaps are extended which changes the mean aerodynamic chord of the airfoil, deflecting the downwash further.  


                                            

The tail is an inverted airfoil, so this downwash angle increases the angle of attack of the tail surface.

This is why you feel the need for forward trim after flap extension in most high wing aircraft. 
 
Now lets look at a sample weight and balance problem.

Two 200lb adults and full fuel in a Cessna 182Q:


Add up the weights and moments:



And note that while we are in the Center of Gravity envelope, we are very close to the forward limit:



The common explaination for wheelbarrow landings in the Cessna 182 is poor technique and pilot induced oscillation.  

Could it be that under reasonable circumstances, the airplanes are often flirting with their forward CG limits? The tailplane stalls as the pilot applies up elevator in ground effect; and the nose drops to the runway suddenly?

It is speculation but I believe you see more nosewheel damage and flexed firewalls on the high wing Cessna's than the low wing Piper Indians ...