Everett Rogers' diffusion of innovation is still massively relevant today. What has changed is the speed with which ideas and products spread. It's worth further exploration but perhaps the distribution of people within each group might have also changed. With technology more of us are becoming innovators. The lines between creator and consumer have blurred. We all increasingly co-create. Facebook is spreading through society, but the big question is where is it in its cycle? That will make all the difference to its prospects.