Felix Salmon, in "The economics of kissing-and-telling," asks several interesting questions but provides no answers.
Eugene Robinson at the Washington Post quotes a colleague's "theory about philandering":
Roberts postulates that famous, powerful men who stray would be smart to choose women who have just as much to lose if the liaison were exposed. Some ultra-rich tycoon's young trophy wife, say, would fit that criterion. Cocktail waitresses and nightclub hostesses, not so much.
Which sounds like a good example of a theory by Nobel Prize winner Oliver Williamson in "Credible Commitments: Using Hostages to Support Exchange," American Economic Review, Sept. 1983. (Very short summary here.)
Remember where you heard it first: the public relations spin--which is taking surprisingly long to develop--will turn out to be that it was all the fault of Ambien.