Good point, Kaph!
I don't think it happened so much in BB1 and BB2, but you're absolutely right - especially in BB4, there was a very quick seggregation of 'girls' and 'boys' who quickly bonded together and then bitched about each other in the separate bedrooms. And I think that definitely affected the way housemates voted, whether deliberate or not.
A boy out first this year? Why not!
