  In the context of non-critical Liouville strings, we clarify why we expect
non-quantum-mechanical dissipative effects to be of order E^2/M_P, where E is a
typical energy scale of the probe, and M_P is the Planck scale. In Liouville
strings, energy is conserved {\it at best} only as a statistical average, as
distinct from Lindblad systems, where it is {\it strictly} conserved at an
operator level, and the magnitude of dissipative effects could only be much
smaller. We also emphasize the importance of nonlinear terms in the evolution
equation for the density matrix, which are important for any analysis of
complete positivity.
