I think the reasoning behind it is, if you cut your power down to 50-60% of your normal use and most people did this - then the electrical demand would drop enough to allow more grids to be turned on. Of course, people are like "what blackout?" as soon as they get their power back on and could care less - I had people next door running 2 air conditioners for a 700-sq ft apartment!

Even worse was seeing some commercial signs downtown flashing away (did you even see Times Sq in NY - lights out for a lot of people - and they got their stupid ad signs flashing away?!).
There is a lot of wasted power out there. For example, the shopping center beside my apartment has a huge parking lot that is never more than 30% full at peak. At night, they have a whole set of lights (which shine into my window OFC) that they don't all need. They could easily go with half of them turned on and still have sufficient and safe lighting for their entire lot.
Anyways, it's late, but I would really like to see more renewable forms of energy being developed. I wonder if anyone has ever thought of putting a few solar panels & storage battery on traffic lights for these situations. At least it could provide enough power to operate the signals on most days, plus store enough energy to go through most of the night...