I agree that the image of bi men bottoming is a little hotter ;)
Though my favorite "bi-scenario" in yaoi is when a young divorced/widowed father falls in love with a gay man and tops o///o

I began writing slash because it's something I never can be apart of myself. Like I can be a man or a woman or even two men, but I can never experience a male/male relationship. Maybe it's the mystery that beckons?