In 1978, a psych prof at FSU was discussing gender differences and suggested to his class that men have a much harder time getting casual sex than women do. His female students were incensed and one even hurled a pencil at him. He set up an experiment, now legendary, in which student volunteers asked strangers for sex. 75% of males and 0% of females accepted the casual sex offer.
The study results have never been replicated, but 35 years later there are amusing YouTube videos making the rounds that once again explore the willingness of strangers to accept an offer of sex.