Future or fad?

I'd like to explore briefly whether the Social Networking 'phenonema' is a fad or an integral component of the future digital society. Personally I think it's the future but others disagree.
Even if social networking overall is not a fad, individual site/experiences could well be virtual hoola hoops.
Op-in Advertising. In the opt-in world of social networks, will a new opt-in model develop for advertising ?
It'll be a fad if money isn't made from it on a broader scale.