  In an earlier publication we had given an exhaustive analysis of the criteria
for weak value measurements of pure states to be optimal in the sense
considered by Wootters and Fields. We had proved, for arbitrary spin cases,
that the measurements are optimal when the post-selected state is mutually
unbiased wrt the eigenstates of the observable being measured.Here we extend
the discussion to mixed states. For these, weak value measurements have several
problems which we illustrate with the protocol proposed by Shengjun Wu. We
discuss tomography of mixed states based on weak measurements and show that
while the principal results of Wootters and Fields hold, namely, the set of
observables needed for complete tomography are such that their eigenstates form
a mutually unbiased bases, weak tomography removes a serious lacuna from the
Wootters and Fields analysis i.e the need to consider only state averaged error
volumes or information. We also consider another proposal for weak tomography
of mixed states by Lundeen and Bamber, and reach similar conclusions about MUB.
