I do remember noting that a few months back when 
someone started a thread about "show me your 
bishounen" and another "show me your bishoujo" 
there were about three times as many posts to the 
bishounen one, mostly by starry eyed female 
collectors.  While I don't think it can be argued 
that general anime fandom is still somewhat 
heavier on the male side, I kind of consider cel 
collectors part of the hardcore fanbase.  You 
have to be to spend that much money on a piece of 
plastic and paint (and yes I know they're more 
than that .. I mean I collect too after all 
^_^).  But there seem to be a much higher 
percentage of people here in this forum than in 
general anime discussions who are familiar with 
obscure anime and anime only released fansubbed 
and whatnot.  I know there are also several cel 
collectors who are also doujinshi collectors (and 
boy lets not get started about now many more 
girls I see in that than guys!), which kind of 
falls into the same "a bit more crazed than your 
average fan" category.  
I also once had a conversation with one of the 
cel dealers, who said nothing flies off his 
updates quicker than bishounen cels.
So perhaps girls on the whole are just a bit more 
likely to get wound up and obsessed in their 
hobbies (and please dont take offense to that, I 
say it only because I -am- a girl and it 
certainly applies to me!) which to some degree 
evens out the general anime gender imbalance?