Others experience an internal (or external) embarrassment and begin acting anxiously as if the person sitting across them can read their minds. In contrast, others experience an anticipating tightening of things low in the body, knowing that the juicy bits are about to come (pun intended).
Few individuals discuss talking nasty, yet many people consider it. Even in today's free information society, few people feel comfortable discussing sex openly and publicly. People may tell their close friends about their latest exploits, but few will bring it up in a typical out-in-public conversation unless euphemisms are used. While you can read about a friend every second of every day on Facebook, sex is a topic few are comfortable discussing. Sex occurs.