Personally, I don't find group sex to be all that sensible or practical.
From the disease-distribution perspective, group sex generates an
exponential increase in infection risk. In one on one, you're not going to get infected by the girl you didn't sex because the girl you did sex also sexed the man that sexed the infected girl - at least, not in the same sitting. In group sex, there's not even a need for incubation, it only takes one diseased cell to infect you, you're just as likely to catch it straight from the same gender via a vector. Speaking of which, lesbian sex is actually a bit more dangerous [http://std.about.com/od/stdsspecificcommunities/a/lesbiansafesex.htm] than heterosexual due to belief contraceptives are unnecessary. In group sex, you'd best wear your contraceptives like you're wading into a small communal sewer: you demonstratively are.
From a social ramifications perspective, group sex introduces quite a number of awkward factors:
- - Exactly how serious is your relationship here? Apparently not much, seeing how apparently there's a need to double up.
- Intimacy? Stop trying, darling, this is a public spectacle and you know it.
- If you meet Ms. Right, would she take offense to having heard of your sorted past?
- Whoops, somebody got pregnant... now, who's paying the child support?
- What do you mean you won't submit to DNA testing and the state backs you up in saying I'm the legal father... nobody in either of our families have red-hair?
- Yes, child I adore? Who's your father? About that... we're still deciding. Please stop cutting yourself.
- Whoops, one bum contraceptive and it seems I got two people pregnant... uh, I can't afford that.
- Hi mom and dad, long time no talk, so anyway, funny story...
From a pleasure standpoint, are more orifices better than one? I suppose you have the luxury of a comparison but, from a sheer technical standpoint, we're not a polygamous species. One on one is nice and intimate. Throwing more at it, you lose the intimacy, you're now put under social performance anxiety, and to do it all for an orgasm comes off as a little desperate.
Have I ever fantasized about being with more than 1 girl at a time? Sure, but fantasy is just that - unlike reality, my imaginary partners never have STDs and are my own personal harem. I prefer to keep my line between fantasy and reality in tact, as this tends to avoid a wide number of serious consequences. In the end, best leave group sex to porn stars, professionals who are well monetarily compensated to bear the realities of it [http://latimesblogs.latimes.com/lanow/2009/06/at-least-16-previously-unpublicized-hiv-cases-in-porn-film-performers-public-health-officials-say.html] for us so we can enjoy the fantasies without that burden.