  The cosmic rays spectrum has been shown to extend well beyond 10^20 eV. With
nearly 20 events observed in the last 40 years, it is now established that
particles with energies near or above 10^21 eV. No nearby astrophysical object
has been shown to correlate with the arrival directions of the highest energy
events, yet the exponential cut-off in the high energy end of the spectrum one
expects to see in the case of far sources is not visible. It was recently
pointed out that the influence of the vacuum of quantum electrodynamics on
particle propagation could explain qualitatively this mystery. This note is a
critic to these ideas.
