I actually just did this experiment at a local museum recently.  Your weight is equally distributed over the "bed of nails" so that you don't give an individual nail more than the 2 lbs. (or a bit more depending on the clothing one is wearing) necessary that it takes a nail to pierce your skin.  \n\nIt's an odd sensation because while you can feel the nails, they don't hurt...definitely something worth trying out if the opportunity arises.