I really believe that most sexually active people have it, but it doesn't always manifest in the form of outbreaks. Think about it. Almost everyone has had a cold sore/fever blister. That is herpes right there. It's usually transmitted by skin contact. Obviously, we won't kiss someone with an obvious sore, so it's probably transferred while dormant/shedding. Some people may never have an oral/genital outbreak, so it's probably much more prevalent than we know.
And yes, even the great Rocco Siffredi has it...LOL