Can we truly have light infantry?

We talked earlier about a new series of tactics for Afghanistan which meant that armoured vehicles were actually detrimental to counter-insurgency, and we've also discussed the fact that mechinization hurts counter-insurgency efforts.  But it's worth examining again with even more evidence.  Indeed, keep in mind that counter-insurgency principle regarding force protection, which states that "the more you protect your forces, the less secure you will actually be".  (This also has paralells with public diplomacy)

Concern over the number of casualties in Iraq and Afghanistan has led to massive increases to the amount of body armour being worn by our Soldiers in an effort to enhance force protection.  The average Soldier is currently being outfitted with approximately 35 pounds of body armour.  When one adds in the amount of ammunition, water, night vision goggles, batteries, and weaponry that the average rifleman might carry, you're looking at approximately 60 lbs per Soldier for a "light" patrol, with even more added for those who carry assault packs, radios, or heavier weapons.

In the 120F heat of Iraq, it doesn't take long for a Soldier to reach the point of exhaustion.  Also consider that in Afghanistan, Soldiers hike up and down mountains that can reach up to 12,000 feet above sea level.  Marine Sergeant Michael Hanson had chimed in on Small Wars Journal that he felt that Marines, in order to truly be a light fighting maneuver force, needed to (among other things) scale back on the amount of armour they had to carry.  Exhausting Soldiers and Marines on a 4-hour presence patrol isn't the way to establish an enduring presence among the local population.  The added body armour has plenty of disadvantages on the battlefield:  while reasonably  effective at stopping rounds, they make American troops slower and more cumbersome.  Indeed, many insurgents wearing little more than cotton pants and shirts are able to outrun and escape from a fully-armoured Soldier.  

The force protection mentality has also invaded vehicle design.  According to many reports (links within this thread), up-armoured HMMWVs are experiencing transmission problems driving up and down the mountains of Afghanistan, and have trouble negotiating the small trails which link together many of the villiages of the region.  The new Mine Resistant Ambush Protected vehicle, or MRAP, has virtually no off-road capabilities, performing well as a Road Warrior vehicle in Iraq, but for little else.  The aforementioned Sergeant Hanson quipped in his article that the military's solution to defeat IEDs was to design a heavily armoured vehicle that is only capable of driving where the IEDs are actually located. 

Focus:  How much armour is enough?  There seems to be a great deal of personal choice (mounted Soldiers prefer more armour while dismounted prefer less armour), but surely there's a happy medium.