David Letterman is now a legal time bomb for CBS. Because of his hijinks, it's only a matter of time before some female staffer who didn't get a promotion will sue for a “sexually intimidating environment” or some similar complaint.
It might be worse if you were a female staffer who did get a promotion while working for Letterman, since the default assumption – rightly or wrongly-- is now that you've slept your way to the top.
Which is one reason why we're supposed to take sexual harassment laws seriously. Or at least we used to, in the good ol' pre-Clinton days.