Thanks for each and every post. Apologies for causing offence, but I think this post sums up better than my own post what I was questioning, and wanted explaining...
To be fair to the OP, I think she was confused and was assuming that bisexuality meant that a person needed to have sex with both men and women to feel sexually fulfilled not that she thought only heterosexual people could be monogamous.
There have been a fair few posts with this tone:
I'm bisexual, monogamous and married to a man. The implication that I will cheat on him due a crazed lust for the ladies is kind of insulting, to be honest. I'm sure you didn't mean it that way, but the assumption that all bi people cheat is a bit like the assumption that all gay men are promiscuous - it's damaging and untrue.
In response to the above post, I wasn't implying that. I find your suggestion that I implied that equally insulting, tbh. Being monogamous is a choice regardless of sexual orientation, just as choosing to cheat on your partner is also a choise.
I said this: if you are bi-sexual, can you be completely sexually satisfied if you choose to be monogamous, or will you always feel that you are missing out on something, iyswim?. I genuinely don't see how that can be interpreted as me suggesting that you'll cheat on your DH, no matter how many times I re-read my OP.
It is also untrue and insulting to presume that bisexual people fancy EVERYONE because they are attracted to both genders! I agree. It's also insulting to me to say that I have presumed that. I haven't!
Thanks to everyone, but I really feel strongly about this so...
Warning rant to follow!!!!
As usual on MN, there are genuine people who try and understand and help, and read the OP carefully and take it at face value. And then there are those who read it, and then revert to their own ideas of what people are thinking. If the OP doesn't fit, just twist it, and then you can carry on regardless, accusing people of making assumptions that they haven't made, and being insulted by things that have never been said! 
Some people on MN are just so fucking determined to be insulted, aren't they? Even if it means they have to make stuff up to justify it!
By the way, I now understand a lot more than I did before, so thank you again to everyone who has posted.