This is getting into heavy mystikal shit.
I'm asking you how this seemingly goldbergian contraption called non-mining node help to keep burglars out of our safe, and you reply "economics and the human factor."
My hands just drop, really.
This is now a different question. Perhaps you believe that all the questions you are asking are the same, and you are merely rephrasing them? This is not the case. I can't keep holding your hand explaining things to you.
A good place to start to understand the role Full Nodes have is here -
http://shop.oreilly.com/product/0636920032281.doThe book is available for free as well.