  If black hole formation and evaporation can be described by an $S$ matrix,
information would be expected to come out in black hole radiation. An estimate
shows that it may come out initially so slowly, or else be so spread out, that
it would never show up in an analysis perturbative in $M_{Planck}/M$, or in 1/N
for two-dimensional dilatonic black holes with a large number $N$ of minimally
coupled scalar fields.
