You believe it's much rarer than female bisexuality, or you believe there are literally zero instances? If you met a man who had slept with several men and several women and continued to sleep with both, what would you tend to assume about his sexuality?

I am a male bisexual. I believe this with a high level of probability, primarily due to my ability to have erections from naked or sexual pictures of both genders. Also the fact that I have felt heavy romantic interest for both genders would seem to indicate that this is very possible.

If you want documented research done into male bisexuality, look into the research of Alfred Kinsey. He researched all forms of sexuality extensively, and was a male bisexual himself.

Edit: Also, the society I have been raised in has practically no instances of homophobia, so I don't believe that could be a factor.

Define bisexuality.

Voted up from -1 because I want you to clarify. Do you believe that bisexuality in women is ubiquitous, while not ubiquitous, but present in some men? Or that it is completely absent in men, but present though not ubiquitous in women? Or any other combination of absent, present or ubiquitous in either women or men?

From your other comments, I believe you're confusing "I don't believe men who say they are bisexual" with "I don't believe men can be bisexual."

It's clear to me that, in American society at least, the majority of bisexual men are to be found among the ranks of men who would never identify as anything but straight, sometimes even to the men they have sex with(!). Conversely, many of the men that DO identify as bisexual are merely finding a graceful way to transition to a homosexual love life.

Thus, that a man who identifies as bisexual is mostly likely gay may be true (though I doubt it--especially among men who have been out as bisexual for more than, say, 5 years) is not an indication that male bisexuality doesn't exist--only that self-professed bisexuality is scantily coterminous with a bisexual orientation in males.

Being wrong in the way that you are wrong will probably not damage the accuracy of your insight when conversing with individuals about their sexuality (you'll correctly assign a high probability to his being gay if he says he's bisexual), but it probably WILL damage that accuracy when analyzing human populations in the abstract (you'll incorrectly assign a low probability to the existence of large ranks of males who engage in and enjoy sexual relations with both men and women).

If it's not against the implicit rules of this thread to ask, on what evidence do you believe this?

BTW, it may not be obvious, but I can tell you that ciphergoth is not talking about a hypothetical example.