The electricity grid is also extremely complicated system that many people don't understand. With any complex system, it grows to beyond the knowledge of the people working in it.
One thing to note is that many of the critical components on the electrical grid is controlled over the network. When I used to build tools for the electricity trading desk, we were handling market bids/asks and scheduling of the power plants.
Here's an example of the stuff that we were dealing with. This is the real time settlement point prices for ERCOT (the grid network in Texas): http://www.ercot.com/content/cdr/html/real_time_spp
We had systems that lay out prices that we were willing to turn on and ramp up power plants. If prices hit a certain point, we were committed to delivering that power. We made these decisions based on economics of the power plant (gas plant vs nuclear vs wind) and other factors (such as weather , time of day, whether the Cowboys were playing that day).
Anyways, my point is that all these systems are interconnected and rather complex. It doesn't take much for an error in one place to bring down a major part of the system.
Take a look at the 2003 Blackout: http://en.wikipedia.org/wiki/Northeast_blackout_of_2003
As with any engineering, you're never going to factor away all the breaks. You need to build a system that assume things will break and ensure that it's not catastrophic.
Also, I don't think it's fair to say that Wall Street doesn't understand software. There are some very smart people doing solid engineering there. Neither one of the footnotes that you had in your post support your statement that Wall St doesn't understand software.