This is actually a very good point I've foolishly overlooked. Yes it'd seem from reading logs of blown up business ventures that pretty much everyone is stretched out to the maximum, like melted cheese, and a ten bitcoin mispayment is the difference between "business as usual" and complete financial collapse.
Still, I wonder if the extreme vulnerability of most participants actually means the (relatively) invulnerable exercise any degree of control. It'd seem to me that it's not the case that "a fairly small number of people have enormous influence over which Bitcoin enterprises succeed" but moreover that "a fairly large number of people have disproportionate influence over how soon their Bitcoin enterprises fail".