  Recently it has been suggested by S. Carlip that black hole entropy can be
derived from a central charge of the Virasoro algebra arising as a subalgebra
in the surface deformations of General Relativity in any dimension. Here it is
shown that the argumentation given in Section 2 of hep-th/9812013 and based on
the Regge-Teitelboim approach is unsatisfactory. The functionals used are
really ``non-differentiable'' under required variations and also the standard
Poisson brackets for these functionals are exactly zero so being unable to get
any Virasoro algebra with a central charge. Nevertheless Carlip's calculations
will be correct if we admit another definition for the Poisson bracket. This
new Poisson bracket differs from the standard one in surface terms only and
allows to work with ``non-differentiable'' functionals.
