  The generalized second law (GSL) of black hole thermodynamics states that the
sum of changes in black hole entropy and the ordinary entropy of matter and
fields outside the hole must be non-negative. In the classical limit, the GSL
reduces to Hawking's area theorem. Neither law identifies the specific effects
which makes it work in particular situations. Motivated by Davies' recent
gedanken experiment he used to infer a bound on the size of the fine structure
constant from the GSL, we study a series of variants in which an electric test
charge is lowered to a finite radius and then dropped into a Schwarzschild, a
near-extremal magnetic Reissner-Nordstrom or a near-extremal Kerr black hole.
For a classical charge, we demonstrate that a specific "backreaction" effect is
responsible for protecting the area theorem in the near-extremal examples. For
the magnetically charged Reissner-Nordstrom hole an area theorem violation is
defused by taking into account a subtle source of repulsion of the charge: the
spinning up of the black hole in the process of bringing the charge down to its
dropping point. In Kerr hole case, the electric self-force on the charge is
sufficient to right matters. However, in all experiments involving an
elementary charge, the full GSL would apparently be violated were the fine
structure constant greater than about order unity. We argue that in this case a
quantum effect, the Unruh-Wald quantum buoyancy, may protect the GSL.
