I’ve found that location & environment are big factors. For example, I’ve had far more bad outcomes off Craigslist, bookstore, and bathhouse hookups than with parties on BBRT and monthly orgies hosted my my friends or me. I suspect that’s because people take more risk and have less concern for others in truly anonymous situations.
On the flip side, communities with ready access to testing & treatment (e.g., San Francisco, Los Angeles, Portland, Seattle) have lower incidence of transmission. Communities with positive sexual attitudes tend to be more aware of symptoms and definitely more proactive with testing & partner notification. For example, a buddy got fucked by over 300 guys in a week in Berlin and came home clean. During his first play session after getting back to Austin he contracted gonorrhea. Very frustrating!
That said, play buddies & I have taken 20+ loads during adult bookstore sessions and usually come home clean. Playing at noon & 5pm helps, because you mostly get married & partnered guys who are careful about not bringing surprises home. So they get regularly tested & treated.