I've been mulling over this labeling business recently. I've been contentedly self-labeling as lesbian for 15 years. However, once I began dating SW, my male FWB, I was automatically moved from the lesbian side of the board to the bisexual side in the minds of many people I knew, even though I've been quite open that I still see myself as lesbian. (I put it as amending my dyke card, not throwing it away!)
I guess to many people, even my queer/queer friendly friends, lesbian meant no sex with men, ever, even though most lesbians at some point have had sex with men (including after they come out). I've always understood my sexuality to be fluid so this response from others is profoundly frustrating to me. It takes away my agency to ID myself in ways that make sense to me.
I hope that this is not interpreted as anti-bisexual. Bisexuality is not the problem. It is entirely possible I will evolve into identifying as bi or pansexual (I see definite leanings towards pan in myself) at some point. However, suddenly I seem to be back in grade school where the slightest touch of male cooties makes one contaminated.