  The light scattered by cold atoms induces mutual optical forces between them,
which can lead to bound states. In addition to the trapping potential, this
light-induced interaction generates a velocity-dependent force which damps or
amplifies the stretching vibrational mode of the two-atom "molecule". This
velocity-dependent force acts on time scales much longer than the mode period
or the dipole dynamics, determining the true stability of the bound state. We
show that for two atoms, the stochastic heating due to spontaneous emission
always exceeds the bounding effect, so pairs of cold atoms cannot be truly
stable without an extra cooling mechanism.
