  Resorting to the notion of a stress tensor induced on the boundary of a
spacetime, we compute the conserved charges associated to exact solutions of
New Massive Gravity that obey weakened versions of AdS_3 asymptotic boundary
conditions. The computation requires the introduction of additional
counterterms, which play the role of regularizing the semiclassical stress
tensor in the boundary theory. We show that, if treated appropriately,
different ways of prescribing asymptotically AdS_3 boundary conditions yield
finite conserved charges for the solutions. The consistency of the construction
manifests itself in that the charges of hairy asymptotically AdS_3 black holes
computed by this holography-inspired method exactly match the values required
for the Cardy formula to reproduce the black hole entropy. We also consider new
solutions to the equations of motion of New Massive Gravity, which happen to
fulfill Brown-Henneaux boundary conditions despite not being Einstein
manifolds. These solutions are shown to yield vanishing boundary stress tensor.
The results obtained in this paper can be regarded as consistency checks for
the prescription proposed in arXiv:1001.3598.
