That's not what I was implying (I did offer monogamy as an option). But yes, in the cold light of morning I see that I posted possibly my stupidest comment ever. Sorry everyone.
Bi people do not have a monopoly on fancying more than one person at the same time - straight and gays have the same choices.
Must learn not to attempt writing Profound Truths when tired, and a little drunk.
All good. Still somewhat confused by what you meant by this though:
If you're bi, the only ethical alternatives are threesomes, serial monogamy, or an open relationship, otherwise you're going to be cheating on somebody. And serial monogamy doesn't appeal because it implies a trail of ex-es.
Because most bisexual people just have sex with people of different sexes when single (if they're into that kind of thing) or end up dating who they're dating, which may through out their life be pretty 50:50 or highly skewed one way. Being interested in threesomes (sexual or relationships) or polyamory are very different to being sexually/romantically attracted to both/all genders.
This, right here, has always confused me. If your bi, then by the very definition, your always gonna have two other partners. Otherwise, it would be who your with that would determine how you are. If your with a man, your still fawning over women, and if your with a woman, your still pining for men. It makes no sense to me. Saying your bi suggests, to me, that your always looking for that threeway...
Then you have a fundamental lack of understanding of sexuality in general. Straight people are interested in the opposite sex. Gay people are interested in the same sex. Bi people are interested in both. All people fantasise about other people when in a monogamous relationship.
Being interested in a threesome requires interest in seeing your partner have sex with someone else. If what you want is to have sex with someone of the same sex but not for your partner to have sex with anyone else then you will have to look at negotiating some degree of non-monogamy.
My partner will not have a threesome with me out of fear of the consequences (something I
may be able to change given the right circumstances but we don't have much of a social life). He has given me explicit permission to sleep with a couple of women who were clearly interested in me - separately. Given I tend to be a bit of a top with women and attract straight girls, but have minimal experience, it scares the shit out of me and would much rather share but there you are. Never worked out but not for lack of effort.
Everyone is different - in sexual attraction, sex drive, and degree of natural monogamy. Just accept it's all on a spectrum and stop trying define other people. Especially when the definitions pretty much end up Normal (straight) and Other (all those other freaks who just want to fuck
all the time).