I didn't know there was a bisexual day. Now I do! ( I'm super lesbian ) but I'm always up for supporting any day that celebrates people being proud of who they are.
Karissa, I think there sure was a time when we bi folks were not represented, just like trans people weren't - and still are often - not represented.
I do think more bi people are out and involved though now.
One thing I sure remember - one year when I was in college, I called the contact people listed for this survey or handout I got in the mail. It was about lesbian and gay events and representation on campus. There was no mention of bi or trans folks and <yes, I was ignorant about trans people and to my shame now, didn't ask about trans specifically> but I asked, how come bi folks are included? I said I was bi. The person I talked to didn't believe there were any and became upset that I called.