A blackout caused by hackers is the holy grail, the proof that extra terrestrials exist, the debunking of the Warren Commission, the final evidence that we are truly headed toward conflict with a parallel universe and shape-shifting mercury-blooded agents are among us. After Eligible Receiver after Cyber Spies Penetrated the Grid (and don't forget Aurora) after all the incidents cited in every SCADA security presentation, the hunger for one documented incident is still so strong that remote attendance won't be allowed at an upcoming SCADA Cyber Security Conference. And you can taste in the latest Call for SCADA Security Researchers from Project Grey Goose
I challenge you to try to get an answer to that question. I spent the last few weeks doing just that and ran into one brick wall after another, and I have some pretty decent connections to fall back on. It turns out that private industry, which essentially owns the U.S. power grid, enjoys a protection from public scrutiny that extends even to Freedom of Information Act (FOIA) requests, and they get to decide what falls under that protection and what does not. So who does this secrecy benefit?