The story of Enron is fascinating, and there's a great documentary on it, "Enron: The Smartest Guys in the Room". 
Also, the article fails to conceptualize how little resources might be required to cause actual disruption. A bomb might cause a lot of damage on it's own if lobbed in to a substation or a transformer yard at a power plant, but some common conductive cable and a javelin in a potato launcher cross my mind as a ghetto version of the military device mentioned knocking out most of a nations power grid.
I remember the great ice storm of 1998. Huge amounts of freezing rain coated transmission lines with inches of ice, and the weight toppled hundreds of pylons in the Montreal area. The metropolis and the region South were without power for weeks. And it was January. And Montreal gets brutally cold at that time of the year.
Perversely, you need electricity to run a fuel oil house furnace.
Some people were without it for a month. We wanted to buy a generator for my mother in law, who lived South of Montreal. We lived in New Jersey. We went to the local home depot and bought the last one. The people behind us in line at the store were from Montreal. There were no generators left in the stores from Montreal to new Jersey.
See "January 1998 North American ice storm"
Building power lines takes a lot of land, a long time, and is expensive. Redundancy and excess capacity is going to decrease. The system will continue to become less reliable.
That is not always correct. There are numerous radial lines where the failure of a single transmission line caused numerous downstream substations and customers to experience outages...also, not every substation has 2 transmission/distribution Xfmrs with a Tie...I've seen numerous substations with only 1 Xfmr.
> Redundancy and excess capacity is going to decrease. The system will continue to become less reliable.
You're absolutely correct on this point...