I don't think Earth Hour goes far enough. Rather than encouraging us all to switch off our lights and computers for an hour a year, we need to have an ongoing commitment and culture of reducing our energy use. Driving less, turning computers off when they're not needed, keeping less food in the fridge. Whatever you're doing, you can probably save more energy every day than the 4-cents-worth you save during Earth Hour. Apparently a good way to encourage home energy savings is to print the neighbourhood average usage on electricity bills. People see that as a challenge or a competition, and they react accordingly. If your electricity provider doesn't do this, you should ask them to start.
Mokalus of Borg
PS - I think most electricity providers in Australia do that.
PPS - And why wouldn't they?