I know a few of my old high school friends have played Soggy Biscuit, which is pretty much a circle jerk. And there was this camp thing that some people go to where people used to jizz a lot for jokes. Like some guy fell asleep and they squirted jissoms in his mouth, or they all jerked into a bag and filled someones bed for it. Its a certain type of person, I dunno. Its weird, to me.
Me and some friends did experiment, during highschool. A lot. But it was never more than 3 guys.