I resist this continued disclaiming of 'terrorists' because there's no evidence of it - but I do want to point out that current 'terrorists' do recon on potential attack points to the extent possible without detection or any overt connection to terrorist activity, and this was also a modus in the 911 attacks well in advance. Any nut job will recon his objective.The point that the original story made is a vulnerability exists in the electric grid, and hearing from others over the years this is one of many, but a fairly attractive one for attackers.

I work at a software company where our software is under persistent attack, millions of attempts per day, and we put up the equivalent of shields around transformers, detection, hardening etc etc. Its an ongoing process. We don't consider any random attack the result of terrorists, they are attackers plain and simple. To differentiate software from the electrical grid, by far the greatest number of our attackers are out for financial gain, followed by a fair number doing it for kicks. The attack points used today are different than the ones once used, we've put up sufficient mitigations to prevent or deter (by things as simple as raising the costs or chances of detection) most attacks [CORRECTION EDIT: *DON'T USE] the original attack points. Dedicated attackers will up their game and change tactics - they are pretty smart for criminals, smart enough for the software industry and software using industries to incur billions of dollars of risk mitigation against them.

So if the electrical grid is considered as a system vulnerable to attack, any attack from a lone gunman to a conspiracy with an intention to harm the US, you should take seriously the identified vulnerabilities and take a methodical approach to hardening critical infrastructure from future attack. We know the grid is a potential target for terrorists because of intercepted intel - photos and documents for example describing the grid and how to take it down - but we don't know if this is the act of any specific terrorist organization. It shouldn't matter, unless you can connect it to them. This attack sounds a darned sight more feasible than an EMP, but there is probably a long list of vulnerabilities to address, and it may be number 1 or it could be number 244 in severity or system vulnerability. To me the only folly is in an electric industry that resists the costs to mitigate attacks, that sounds foolish. We all do that now, its the cost of doing business in a turbulent world.