  There are many observational evidences for the detection of compact objects
with masses significantly larger (in galactic cases) or much larger (in
extragalactic cases) than the upper limits of masses of em cold Neutron Stars.
Such compact objects are commonly interpreted as Black Holes (BHs). However, we
point out that while such Black Hole Candidates (BHCs) must be similar to BHs
in many respects they, actually, can not be BHs because existence of Black
Holes would violate the basic tenet of the General Theory of Relativity that
the worldline of a material particle must be TIMELIKE at any regular region of
spacetime. We arrive at this unique conclusion by approaching the problem from
various directions. We feel that such ``operational'' Black Holes could be able
to explain hard X-ray tail found in the galactic BHCs because Lorentz factor of
the plasma accreting on such objects should be considerably higher than the
corresponding NS case.
