While familiar with the limits of the "speed of light", etc., it seems one could use the Casimir effect to send messages across arbitrarily-large distances with carefully-tuned Casimir plates.  

A message could be time-length encoded on a carrier wave of a specific frequency and then transmitted between Casimir plates spaced with the exact wavelength.  Equivalently-tuned plates elsewhere, *regardless of location*, should receive the signal from the vacuum.