Personally my own sexuality is very fluid. If asked to label myself I do claim the bisexuality label (if only for the sake that it is much easier to explain than pansexual or queer). There are times when my interest in one gender is much higher. Then the next week it could flow the other way.
This is not saying that it is the same for everyone, but I don't think it is as clear cut as 50/50 for the majority of people out there. However it is a spectrum so obviously there will be some people out there on the 50/50 part.
It's a spectrum. Very few people are 50/50. I consider myself bisexual despite the fact that I lean slightly toward the same sex, I'm in a hetero relationship. Look up the Kinsey scale.
I think it's a spectrum-for me it's most certainly not 50/50, but I still have the potential and inclination to be attracted to all genders and both sexes. With that said, it's different for everyone.
I'm bisexual, but I'm definitely not 50/50. I'm more 30/70, with guys being the majority... but this is absolutely relative. It just means that among people I find attractive, there tend to be more men that women, but this changes according to the situation and even my mood. There are days in which I will shudder just thinking of being with a man, and days in which I won't even notice the women around me.
For me I think it really depends on who I'm surrounded by at the particular time. While I'm at work I'm surrounded by a lot more male coworkers than women, so I lean towards an attraction of men. However, at the bars or going out with my friends we usually go in a large group of women (which invariably attracts more to our group) and I can hit it off with someone else. The area I live is very restricted for homosexuals, so it isn't always easy to find the right girl for me
Every person is different. I would say I go for women a lot more than I do men. I would say I'm 70/30, being that 70% of the time I'm way more attracted to women. but, like has been said, it depends on the place and who you are surrounded by, guys or girls.
It definitely feels like a spectrum to me. I'm attracted to people pretty much regardless of gender, but it feels like everyone's orientation is a fairly personal thing and people's feelings vary widely, even among those who use the same term to identify themselves.