For the bisexual preference, they spent way too much time studying men and women together. They are obviously different cases, and should have been treated separately.
My intuition is that a bisexual woman is more likely to be into women, and a bisexual man is more likely to be into men. In other words, bisexual people are more gay than they are straight. This is my guess anyway, and if it's right, grouping men and women together in this study, to see who 'bisexual people' seem to like more, is completely useless.
There are people here who could speak to it better than me, but I'll say what I understand from reading different forums and such.
Everybody is on a scale of sexuality. Very few people are 100% straight or 100% gay, but they're close enough that they are effectively whatever they identify as. But bisexuals/pansexuals sit somewhere in the middle of that scale, though not necessarily at the 50% mark. They'll generally lean more one way or the other.
I suspect, though, that a lot of homosexuals will identify themselves as bisexuals, because it's a little easier (I've been told it isn't, though, and I can't speak for others). From the outside, at least, bisexuality seems like a compromise, even though they may prefer the same sex more.
The stats may also be heavily shifted due to people who only make one or two connections on the site, ever, and even though they're bisexual the one or two connections (especially one
) would be the same gender.