Yes, Virginia, there is a bisexual

New study says bisexuals really do exist.

I've never completely understood the disturbing reaction some people have to the existence of bisexuals.  Why not believe they exist?  Why can't someone be interested in both sexes?  Sure, I suspect some bisexuals might be 60-40 or 70-30, in terms of their same-sex vs opposite-sex attractions, and by the time you hit 70-30, I'm not entirely sure you're bi rather than gay with some side interests.  But why can't some be 50-50?

Having said that, this study doesn't seem to prove that 50-50 exists, just some less (more) than 100-0.