According to a recent study by researchers at SUNY-Buffalo, the sperm of men who smoke are weaker and have a harder time breaking through the egg's protective outer layer, called the zona. These smoked, weak-tailed sperm are "up to 75% less fertile" than non-smoked sperm. But maybe that's why chicks dig the smokers: because they know they've got less of a chance getting knocked up by their feeble little sperm.
Fertility: Nicotine Changes Sperm, and Not for the Better [nyt]
Ah, my alma mater makes daddytypes...