Via Hit & Run, a Wash Times review of Landsburg's More Sex is Safer Sex:
The "More Sex" thesis: If prudes occasionally slept with strangers, it would slow the spread of STDs.
Here's how it works. One such prude walks into a bar, and he's uninfected. If he takes home an uninfected woman, great -- he distracted her from a potential disease carrier. If he gets herpes, that's also great, because he's sexually conservative and won't pass the infection along very often. Better him than someone with less self control.
Either way, society benefits when the chaste open up slightly. "Slightly" is key, because too much "openness" spreads more disease than it diverts. After studying AIDS in England, Harvard's Michael Kremer put the cutoff at 2.25 partners per year.
Via my household expert in the mathematics of STDs, I've learned the following: Inefctivity per sexual encounter matters tremendously. (I have no idea whether Landsburg notes this; the review doesn't.) HIV is much, much less infective than herpes. Herpes spreads incredibly quickly by heterosexual intercourse; HIV doesn't. On average it takes a lot more than a one-night-stand to heterosexually contract HIV. If 2.25 partners per year is really the right equilibrium figure for HIV, then the figure for herpes would be a lot less-- maybe two orders of magnitude less.
I'll try to lay hands on the book itself and follow up. But at the very least, no monogamous readers should read this and decide to go have a one-night stand on the theory that they're slowing the spread of herpes...