  Landauer's principle states that the erasure of one bit of information
requires the free energy kT ln 2. We argue that the reliability of the bit
erasure process is bounded by the accuracy inherent in the statistical state of
the energy source (`the resources') driving the process. We develop a general
framework describing the `thermodynamic worth' of the resources with respect to
reliable bit erasure or good cooling. This worth turns out to be given by the
distinguishability of the resource's state from its equilibrium state in the
sense of a statistical inference problem. Accordingly, Kullback-Leibler
relative information is a decisive quantity for the `worth' of the resource's
state. Due to the asymmetry of relative information, the reliability of the
erasure process is bounded rather by the relative information of the
equilibrium state wit respect to the actual state than by the relative
information of the actual state with respect to the equilibrium state (which is
the free energy up to constants).
