On the dynamic nature of charge quantization
  It is commonly observed that objects in a gravitational field experience a rate of acceleration that is independent of their mass and that, as a result, all massive objects with the same initial conditions follow the same trajectory. It is not generally recognized, however, that charged particles in an electric field experience an acceleration which is \emph{inversely proportional} to their mass. This dynamical behavior is an interesting clue to the fundamental nature of the electric force, equally as important as the more familiar behavior of falling bodies, and seems to be the true significance of the observed fact that different charged particles have the same magnitude of charge $e$. 
Dennis Crossley
physics.gen-ph