We emphasize, once again, that although P and M can be replaced with equivalent boundcharge
and bound-current densities within Maxwell’s equations, such substitutions are not
allowed in the context of force, torque, and energy. In other words, electric and magnetic dipoles
exhibit certain special properties in their interactions with EM fields that set them apart from
ordinary charge and current distributions. An electric dipole should not be considered as merely
a pair of positive and negative charges attached to the opposite ends of a spring, nor should a
magnetic dipole be thought of as a simple Amperian current loop. With the demise of the
Lorentz law of force, electric and magnetic dipoles acquire individual identities above and
beyond what Maxwell’s equations have traditionally ascribed to them. The essential quantum
mechanical nature of electric and magnetic dipoles is such that their interactions with EM fields
cannot be described in terms of equivalent (bound) charge and current densities; rather, these
interactions are governed by Eqs.(6) and (7) when linear and angular momenta are being
exchanged, and by Eq.(8) in situations involving an exchange of energy.
http://arxiv.org/pdf/1205.0096.pdf


The Lorentz force is fine in vacuum say for single electrons in EM fields at the microscopic level. Einstein showed in 1908 that there are extra-emergent terms that depend on the material's polarization and magnetization at the coarse-grained level inside matter. This is no big deal conceptually - just bad pop science writing by journalists.