This thread & the topic are great. But “labels” or identities only point you to the top of a bell curve. They can tell you as much about sexuality as “100” tells you about the average IQ.
I think the reason sexualities are complex is because brains are complex villages of systems interacting with each other on many different levels. I flirt with other gay guys I have no intention of sleeping with (to revert to the thread's original topic) just for the hell of it, even if we have no sexual chemistry, maybe just to say I like them, or stroke their egos. I flirt with straight guys to annoy and flatter them. Straight & gay guys flirt with me for the same reason, and I'm clear about what they are. I don’t flirt with weak people, male or female, since they might misunderstand. Sex is communicative behavior. You can communicate both who you are and who you are not in sex.
I think all the comments made earlier about labels can be tested if you think about your name (as label) and your identity. Your identity is the peak of a bell curve that outlines the reality of your behaviors, history, potential, etc.. There is a fairly large "population" under the tent the bell curve makes, with extremes to the right and left.
People may point to extreme outliers in me and cite them as proof that my overall identity, at the top of the curve, is false. That’s nuts. In fact, I’m the only one who knows the full range and extent of what lies under the curve--not just the range of what I’ve done, what I could do, and what it means--but of who I want to be and where I'm headed. Others might get it right or wrong. I can make it easier for them by being more transparent about myself, and more difficult by being more opaque.
This is what makes the topic difficult I think, and interesting. The bottom line is that when we identify ourselves, that identity might not be in sync with the way others identify us.
I think the bottom line in sexuality is who we want to bond with, and how. We can’t use outliers or random events to prove or disprove anything. A single event can be at the margins, or in the very center and near the top of our identities, just like a single person is in a population distribution can be at the extreme margins or the very center. We typically do not identify ourselves on the basis of one extreme or random event, no matter how much others might want to use that to their own advantage, and to our disadvantage.