A few years ago all the rage was about carbon nanotubes. An entire generation of phd students was raised on this material. Carbon nanotubes were the material of the future, enabling the space elevator, nanoscale transistors, near-superconductor conductivity and so on. What is left today?
Even before that there were C60 buckyballs, another previously unnoticed carbon allotrope. Buckyballs were set to revolutionize chemistry and were (are) part of n-type organic semicunductors. What is left today?
A fad is a fad, even in science. Of all the imagined applications a few will remain, and will be turned into real applications by technologists and engineers. The scientists will move on to the next fad - well at least those who are quick enough.