Ok I've not read every single post in this thread, so don't get angsty if I repeat something already said or whatever, but this is my 2 cents.
I've seen some posters get shot down in this thread because they're basing their opinions on their own experiences, which obviously isn't representative of the wider public, and is often at odds with others experiences. But surely that's what everyone is doing? We can only have opinions based on our own experiences, so everyone's opinion should be valid and taken into consideration.
So, in my experience, I know very few girls who play games, and of those few even fewer who care enough about it to be regularly vocal, and of those few even fewer who would have actively gone on the internet and searched out a forum to discuss gaming.
Among my friends there is probably a higher percentage of girls who game, but that is to be expected, as a girl gamer myself I am more likely to be friends with people who are into similar things as me. But if I look beyond my social circle, other girls I know (girls I went to school with, girls I work with, friends of friends etc) the amount of girls who play games is a lot lower. And most of those who do game do so with their boyfriends or other friends, the number of girls who would switch on a console when home alone is teeny tiny.
But even those girls I know who do play games are not on here. In fact, as far as I am aware they are not on any forum or internet discussion, apart from facebook where they are all too eager to proclaim themselves gamers/geeks/nerds etc. I just don't think they care enough about it to join an internet forum and discuss games with a bunch of strangers. Girls would prefer to talk about things with their friends.
I was introduced to Neogaf by a male friend, and thought I would give it a go. To be fair I mostly post in OT, mainly the BritGaf OT, but we do still discuss games in there. For me personally, I would say that I am not like other girls, I am aware of this and I am fine with it, but obviously everyone has their own reason for being here. So apart from the obvious I don't think there's any other underlying reason for there not being many girls on Gaf.