I'm bisexual and have climbed back into the closet because of attitudes like displayed on this thread. I am married to a man so people assume I'm straight and it's easier leaving it at that.
As has been said, bisexuals rarely feel exactly 50/50. I do have a strong preference for men but find women sexually attractive as well. I enjoy sex with women but have only met one or two women I would consider an actual romantic relationship with. The women were straight so I have only ever had romantic relationships with men. According to a lot of people that just makes me straight.
If you, like me, have sexual fantasies about women, get turned on by women and find pleasure in having sex with women but consider yourself straight then that's up to you but that doesn't sound straight to me.
I've also been told (by a gay man no less) that I am more likely to cheat and been asked how I can possibly have a relationship with a man without eventually cheating with a woman.
I've regularly been told I'm pretending for attention or to turn men on. I've been questioned in detail about my sexual history including how many women I've slept with and in what context. They ask so they can decide if I'm actually bisexual or not.
Biphobia is very real and I've often had it from the lesbian/gay community as well as straight.
"Obsessed with labels/percentages" is often thrown at us when we are trying to explain something that should be very simple but for some reason is difficult for some people to get their heads around.
Most people can get their head around some people fancying women and some people fancying men. I'm not sure why it gets trickier when it's both, especially when there's a preference there.
Imagine you have a preference for brunettes and most of the people you fancy are brunette. There are still some blondes you fancy, it's just rarer. Well it's like that.
11 is definitely not too young to know. Most of my peers were having their first boy/girlfriends and proper kisses at that age. Presumably they fancied those people.
You can fancy people before you're at the age you're ready to have sex with them. I remember fancying a boy in my class in my first year of secondary school. To me he was so attractive that when he walked in I remember stood there gawping at him. The thought of sex at that age was gross but when he spoke to me I got butterflies and I used to want to hold his hand and be his "girlfriend".
(As it happened, my friend told him I fancied him and when he asked me if it was true, I got scared and denied it. Alas! We will never know if the chance passed me by.)