The point of Earth Hour is public awareness, to get people talking, thinking, discussing solutions.
But it doesn't even do that! At best, a few 'regular people' -might- think about the environment for a few days (or hours), akin to the hype around St. Patty's day this year. But come the day after, those people will forget all about it. And at worst, it just gives environmentalists more to be smug about, sniffing their own asses thinking they are making a difference, when in fact they aren't. We're on hydro-electric here. Our CO2 doesn't change a lick if we turn out our lights in the PNW.
No, Earth Hour is simply a fundraising opportunity for the WWF and other environmental organizations. Its mainly about money, and has little to do about making real change. Similar to politicians and political parties, environmental organizations need to look like they're fixing problems, otherwise they won't make money, or a living. I'd go as far as to say many environmental organizations are also anti-technology (nuclear, GMOs, etc), shooting themselves in the environmental foot they want to fix.
If money can't buy happiness, I guess you'll just have to rent it.