Nut removal after taking a hefty fall can be troublesome, less so from a hang I reckon. Climbers use a dedicated tool as can bee seen in this picture http://en.wikipedia.org/wiki/Nut_(climbing
) . Basically removal is buy pushing the nut in the direction away from how it got lodged. (or pulling the wire/tape)
Loosing a machine nut would be less of problem finacially but hardly leave no trace.
The ultra traditional version of nuts are 'chockstones' natural occuring jammed rocks in cracks that climbers utilized buy tying a rope or tape around. A suspicious ammount of of these 'naturaly occuring' chock stones started to appear in cracks and finaly climbers gave up the pretence and started to use the metal versions. Theres another possible securing method for hammockers then
I was thinking about cams or friends as well, but I dont have any of my own. Tricams
are potentially more adaptable and I believe the camming design aids in their removal and ablity to deal with straight cracks and horizontal loading.