  A conjectured connection to quantum gravity has led to a renewed interest in
highly damped black hole quasinormal modes (QNMs). In this paper we present
simple derivations (based on the WKB approximation) of conditions that
determine the asymptotic QNMs for both Schwarzschild and Reissner-Nordstrom
black holes. This confirms recent results obtained by
  Motl and Neitzke, but our analysis fills several gaps left by their
discussion. We study the Reissner-Nordstrom results in some detail, and show
that, in contrast to the asymptotic QNMs of a Schwarzschild black hole, the
Reissner-Nordstrom QNMs are typically not periodic in the imaginary part of the
frequency. This leads to the charged black hole having peculiar properties
which complicate an interpretation of the results.
