  It is pointed out that the constraint to be imposed to the maximization of
the entropy for processes outside the class of thermodynamical systems, is
generally not well defined. In fact, any probability distribution can be
derived from Jaynes's principle with a suitable choice of the constraint. In
the case of Tsallis's non-extensive formalism, this implies that it is not
possible to establish any connection between specific non-thermodynamical
processes and non-extensive mechanisms and, in particular, to assign any
unambiguous non-extensivity index q to those processes.
