There were points in my career where I knew something was happening and was into certain technologies or communities: Linux, wifi, Drupal, Subversion, Apple Cocoa programming, Twitter, OpenStreetMap, the list goes on. A tiny core of people knew the potential, but 99%+ of the world didn’t know nor care what it was. There were just as many, or more, that died out, but my point is that measuring how many people have heard of a thing is not a great metric.