  We discuss from the condensed-matter point of view the recent idea that the
Poisson fluctuations of cosmological constant about zero could be a source of
the observed dark energy. We argue that the thermodynamic fluctuations of
Lambda are much bigger. Since the amplitude of fluctuations is proportional to
V^{-1/2}, where V is the volume of the Universe, the present constraint on the
cosmological constant provides the lower limit for V, which is much bigger than
the volume within the cosmological horizon.
