  The aim of this paper is to revisit the calculation of atom-surface quantum
friction in the quantum field theory formulation put forward by Barton [New J.
Phys. 12 (2010) 113045]. We show that the power dissipated into field
excitations and the associated friction force depend on how the atom is boosted
from being initially at rest to a configuration in which it is moving at
constant velocity (v) parallel to the planar interface. In addition, we point
out that there is a subtle cancellation between the one-photon and part of the
two-photon dissipating power, resulting in a leading order contribution to the
frictional power which goes as v^4. These results are also confirmed by an
alternative calculation of the average radiation force, which scales as v^3.
