Often referred to as the "invisible majority," several studies indicate that self-identified bisexuals make up the largest single population within the LGBT community in the United States. In each study, more women identified as bisexual than lesbian, and fewer men identified as bisexual than gay.
In a 2010 study published in the Journal of Sexual Medicine found that among adults (5,042 respondents), 3.1 percent self-identified as bisexual, compared to 2.5 percent who self-identified as either gay or lesbian.
The Advocate discusses why we need Bi Pride Day:
I was a 14-year-old outspoken, feminist extrovert, but I somehow allowed other people to tell me how I felt or tell me that my sexual orientation was of less value. I let myself believe that bisexuality wasn't real or was greedy or that coming out was pointless, because other gay and straight people believed it. But at the very least, the anger that I still feel over this is what drives me to wake up and come to work at this publication every day. [...]
So, if you were wondering, that's why we must have Bi Pride Day. So that actual bisexual people can own their sexual orientation and feel like we're not just sitting on a fence or can't decide or that we're disappointing someone. Bi Pride Day exists so that some teenage kid who doesn't quite get what she's feeling can see that she's not crazy and she's not going through a phase.
On a related note, thanks to Andrew Sullivan for mentioning the celebration-worthy literary tryst between Oscar Wilde and Walt Whitman:
Oscar desperately wanted to meet Walt Whitman, whom he and many others considered to be America's living poet...Whitman's poetry spoke of the potency of friendship and love between men, particularly between working-class men, and positively oozed homoeroticism. Indeed, the 'Calamus' section of Whitman's great poetic cycle Leaves of Grass was so intensely homoerotic that it gave rise to the short-lived term 'calamite' to denote a man who loved men. Swinburne was to denounce 'the cult of the calamus' and 'calamites.' [...]
Oscar was suitably humble in the presence of Whitman, greeting him with the words, 'I have come to you as one with whom I have been acquainted almost from the cradle.' The contrast between the two poets could not have been more marked. Oscar was young, tall, slender and clean shaven. Whitman was in his early sixties, but looked much older. He was shorter than Oscar and wore a long, bushy white beard. Oscar was highly educated, cultivated and still in his languid Aesthetic phase. Whitman was self-taught, and robustly masculine in manner. [...]
Stoddart tactfully left the two poets alone. 'If you are willing - will excuse me - I will go off for an hour or so - come back again - leaving you together,' he said. 'We would be glad to have you stay,' Whitman replied. 'But do not feel to come back in an hour. Don't come for two or three.' Whitman opened a bottle of elderberry wine and he and Oscar drank it all before Whitman suggested they go upstairs to his 'den' on the third floor where, he told Oscar, 'We could be on 'thee and thou' terms.'
The next day, Whitman told the Philadelphia Press that the two of them had a "jolly good time" together. Did he get more specific? He did, reader. He did:One of the first things I said was that I should call him 'Oscar.' 'I like that so much,' he answered, laying his hand on my knee. He seemed to me like a great big, splendid boy. He is so frank, and outspoken, and manly. I don't see why such mocking things are written of him.
Later, this tidbit emerges:
Oscar told [his friend George] Ives that there was 'no doubt' about Whitman's sexual tastes. 'I have the kiss of Walt Whitman still on my lips,' he boasted.
For more, see Neil McKenna's book The Secret Life of Oscar Wilde: An Intimate Biography (pp. 31-33).