Here's a question, would the girls prefer all the cute guys to be bi or gay?  
 
I dunno, I know a lot of girls that seem to think two guys kissing is cute, and I know a bunch of girls that are yaoi (sp?) lovers too.  Of course, I also know a lot of girls with pictures of when they were drunk and were talked into kissing another girl, so who knows.  ^_^  Happily, none of them have tried getting me to kiss a guy or anything, but some have said they'd have a guy that's "perfect" for the thing and would want me to let them know if I was going to so they could see/take a picture...I have to wonder how much of that is fantasy and how much of that is reality.  I mean, really, what sexuality is it when you want to see two people of the opposite sex doing each other?  (A question I've asked guy friends who have this idea that lesbian porn is so hot.  To me, it doesn't make all that much sense for a guy to want to see two girls or a girl to see two guys, unless they think they are going to get to join in or something...well, or if they think it's cute or like the asthetic value of it...)
I think ultimately, the danger of your partner going outside of the bedroom is the same whether you're gay, straight, or bi.  The only difference is that people may think that bis have more options to go to.  Truthfully, if there's something wrong in your relationship or sexual relationship such that the person is willing to go out of the bedroom for males, females, or both, then the problem isn't them being bi so much as it is a deeper problem in your relationship...well, there are the cases where the person just "felt like" putting it in a vagina one night or "felt like" getting it on with a guy, and their current partner was simply not equiped with the proper parts to fulfill that need.  So that could potentially be a partial truth hidden in the stereotype.  But again, excepting that (the phisical limitations of you being one sex or the other), if you're doing what you're supposed to to have a healthy physical, emotional, and mental relationship with your partner, then you shouldn't need to worry about what their orientation is, as they know to come to you when they need to be satisfied.  ^_^  But maybe I'm just thinking about it too logically...