I tend to agree with the orginal poster.
The first time we swung, I had NO idea who was sucking my dick (with a woman sitting on my face). A guy sucked my dick without my knowledge, so does that make me bi?
When a woman is riding my face and I'm getting the best head of my life, am I going to care if it is a male or female who is doing the sucking? Never even entered my mind at the time!
My experience at the Chicago area clubs is almost ALL single guys wanting to be with a couple are open to m/m contact during a 3some. The same goes for AFF and other swing sites.
Just as an experiment on AFF, I put up two profiles, one as a bi couple and the other as a straight couple looking for a male to join us. Pretty much the same group of single guys replied. Many stating, "my profile says straight but I would want to suck your dick." In their response to the other profile, they were completely straight!
My guess is 80-90% of single guys looking for couples are bi to some degree.
With couples, I was suprised how many guys are bi. When we meet other couples, we do tell them that we are OK with m/m contact, but do not expect me to recripcate. We have been with about 30 couples, alot of "straight" men wanted to feel or suck my dick once I told them I was open to it. My guess is only about 10% admit being bi when asked, but behind closed doors with an couple who is accepting of the other guy being bi and it jumps up past 50%.
I always felt I was 100% straight until I started swinging. I still am very passively bi, but it certainly doesn't bother me if a guy wants to feel my dick and size me up before I give his wife the ride of her life... If he wants to suck his his wife's juices off my dick when I'm done, more power to him.