Earth Hour ; Sensible or nonsensical ?

Is it worth the one hour on the 28th of March at 8.30 pm whereby 80+ countries will participate in this noble event ? I'm not sure ...

Shawn : Why insaf for an hour and then waste for a whole year ?
Sean Chung : Dunno lar
Myself : Am interested in joining just for the fun of it ..

But seriously , can someone really tell me the true meaning of this event ? Hopefully , a detailed one ..

HD