That point was made evident to me when she showed the 3 games.. A game where to win you have to survive an oil shortage? It's virtual but the point is the things you do in the game will seep over into the real world, therefore changing the world before we have an actual shortage if enough people play the game and it's designed well enough for maximum seepage.
I think it's an interesting idea (like most things at TED) but hard to imagine it being accepted... I especially don't like all the talk about WoW as I think (and as evidenced by this thread) that REALLY detracts from the important part of the conversation because of all the negative things that can come from spending too much time/energy on it... WoW is designed to make you play more and more because it's driven by money, I would assume a "world changing game" wouldn't have these hooks and you wouldn't have the issues associated with people wanting to play 12 hrs or more a day or whatever.