wow, thats incredibly scary. Would you only know that once its too late? How would it be corrected? Again...very scary..
Some more detail from the Wikipedia entry[0]:
"On 2 June 2013, investigators from the Ministry of Transport and Civil Aviation of Afghanistan confirmed the load shift hypothesis as the starting point: three armoured vehicles and two mine-sweeping vehicles, totalling 80 tons of weight, had not been properly secured. At least one armoured vehicle had come loose and rolled backwards against the airplane's rear bulkhead, damaging the bulkhead. This also crippled key hydraulic systems and damaged the horizontal stabilizer components - most notably the jackscrew, which rendered the airplane uncontrollable.[10] Control of the aircraft was therefore lost, with the abnormal pitch-up rotation, stall, and crash to the ground ensuing.[1] The damage made it impossible for the crew to regain control of the aircraft."
[0] https://en.wikipedia.org/wiki/National_Airlines_Flight_102
I'm not familiar with airline operations because I've never flown anything bigger than a Cessna 172, but from what I gather the airlines assume an average per-passenger weight, and account for number of bags and the ground crew will distribute in the holds accordingly. Ever seen flight crew moving passengers on little regional jets? It's to make the weight distribution safer. The smaller the plane, the bigger the effect of a few passengers.