  I comment on Ulvi Yurtsever's result, which states that the entropy of a truncated bosonic Fock space is given by a holographic bound when the energy of the Fock states is constrained gravitationally. The derivation given in Yurtsever's paper contains an subtle mistake, which invalidates the result. A more restrictive, non-holographic entropy bound is derived. 
Entropy bound and local quantum field theory