  We construct a trajectory-based semiclassical theory of shot noise in clean
chaotic cavities. In the universal regime of vanishing Ehrenfest time $\tE$, we
reproduce the random matrix theory result, and show that the Fano factor is
exponentially suppressed as $\tE$ increases. We demonstrate how our theory
preserves the unitarity of the scattering matrix even in the regime of finite
$\tE$. We discuss the range of validity of our semiclassical approach and point
out subtleties relevant to the recent semiclassical treatment of shot noise in
the universal regime by Braun et al. [cond-mat/0511292].
