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-encoded on a carrier of a specific wavelength and then projected into the "Casimir void" between (rigid) plates tuned to the *same* frequency.  Any other equivalently-tuned plates, *regardless of location*, should receive the signal from the vacuum.