It might look good as a "light show" for the Television and the Newspapers, but it is tokenistic, and a stunt.
It is good publicity for the marketing gurus of WWF, but they are flogging it as an ego trip for themselves (Earth Hour has "gone global"). It will do nothing for the planet. But it will do wonders for the CVs of the individuals in WWF.
Expect them to progress in Marketing, Advertising, and Politics and the other Trivial Arts of self-serving commercialism.