Dunno but there's a picture floating around of where a suicide bomber tried to take out a Bradley and left a stain on the Bradley
On top of which, the largest load a man could carry and still run at a tank, unless formed into a shaped charge and aimed accurately, won't do much of anything.
The car bombs with which the terrorists are targeting our forces in Iraq are of the 100kg-plus class. That's over 220lbs, more than your average human is going to be able to carry for any distance, let alone run.