  Swift J164449.3+573451 is an exciting transient event, likely powered by the
tidal disruption of a star by a massive black hole. The distance to the source,
its transient nature, and high internal column density serve to complicate
several means of estimating the mass of the black hole. Utilizing newly-refined
relationships between black hole mass, radio luminosity, and X-ray luminosity,
and de-beaming the source flux, a weak constraint on the black hole mass is
obtained: log(M/Msun) = 5.5 +/- 1.1 (1 sigma confidence). The confidence
interval is determined from the current intrinsic scatter in the relation,
which includes effects from X-ray variability and accretion modes. This mass
range is broad, but it includes low values that are consistent with some
variability arguments, and it safely excludes high mass values where it becomes
impossible for black holes to disrupt stars. Future refinements in
relationships between black hole mass, radio luminosity, and X-ray luminosity
will be able to reduce the uncertainty in related mass estimates by a factor of
two, making this technique comparable to estimates based on the M-sigma
relationship. Possible difficulties in placing such events on the fundamental
plane, a potential future test of their suitability, and uncertainties in mass
stemming from variable X-ray emission are discussed. As near and longer-term
survey efforts such as Pan-STARRS, LSST, LOFAR, the Square Kilometer Array, and
eROSITA begin to detect many tidal disruption events, black hole mass estimates
from combined X-ray and radio observations may prove to be very pragmatic.
