Oh, I agree with you there ... electricity will take all paths, and I have also seen some really nice arc paths. Not that those scorch marks mean much; a visit to a weld shop will show you just how much energy can be found in a 20-amp circuit.
What I want to stress in my over-simplified model is the critical need for the ground wires to ultimately be connected - at the service only - to the utility neutral.
Otherwise, you'll get all manner of DIY types thinking they can 'make' 120v at their 240v only well house by simply banging in a ground rod. Visit the DIY forums, and you'll see that this brilliant idea comes up on a regular basis.
Other folks will bond the neutral to the pipe, when there's no neutral wire convenient. A very dangerous practice - even if the two are connected at the main service!
What if there is no connection back to the utility neutral? Just a ground rod? Well, I would never actually test this; I can't think of a safe way to do it. I'll leave that for others to research. Terms that come to mind include 'floating neutral' and 'stray voltage.' If nothing else, we want to make sure that fault current has a much, much better path back 'home' than Mother Earth.
