Well, I will say the thoughts of seeing Steph with someone else (guy or girl) is pretty erotic to me. For me, there's a *big* difference between a sexual encounter and an emotional bond. I try to look at the third person as pretty much a sex toy with a pulse.
Well, either of us being "intimate" with someone else is still a new concept in our relationship, but the boundaries we've set in place are acceptable to us both, and if either one of us felt unfomfortable about something the boundaires are open to being redefined.
I guess the fidelity factors in in that we only find playing with others acceptable if we are both present. Basically, so long as neither of us have a problem with whats going on then its fair game. So long there hasnt been a problem.
I guess this fits as a response to both of you...
Especially when you open the doors to "live sex toys", open and honest communication - and 100% agreement on the rules - becomes critical. (IME)

Granted, it's not really going to happen unless you tell someone about it first, but I'm sure people don't like to be afraid to disclose their sexual orientation.