  Isospin and U-spin symmetries are useful approximations for studying penguin
dominance in $B$ meson decays to three kaons, $B\to KK\bar K$. We point out
certain subtleties in treating these decays in these approximations. Resulting
uncertainties are discussed in determining the CP content of the final state in
$B \to K^+K^-K_S$, and in relating the CP asymmetry in this process to the
value of $\sin 2\beta$.
