Whereas females do not need to do this because they have a strong social and discussion network (thus favouring sites like Pinterest and Facebook which are not discussion based)?

This isn't a bad hypothesis at all. I feel very different at times because of my lack of a strong female group of friends. My mom and girls at my high school all have very strong lifelong bonds. My mom just went to a weekend getaway with girls from her sorority - 30 years later! I suppose if you get all the desired interaction from people in real life, you don't have as much need for an online, discussion based community.

Thinking about it, I see and experience a lot more female interaction based around things that are very specific to their situation. Things like boyfriends, marriage, inside jokes, family, etc. My best friend and I in high school never discussed much besides boys and sex and personal identity and self esteem and the rich town we grew up and resented. If we did talk deeper it was mostly about our opinions (ie: abortion) that weren't really backed up by current events or articles. Perhaps because female's conversations stay more focused on things close to them, an online forum doesn't attract them as much.

When I hang out with guys the conversation can float from politics to video games to articles or television shows we heard/read/saw. Personal opinions on said things are there but are much less prevalent. Guys also don't tend to discuss their emotions or issues regarding self-esteem or desire to have babies or get married or sexual encounters in the same way girls do. Conversations with guys about sex go like this: "I went out with Mary last night." "Oh yeah, how was that?" "Yeah, we had drunk sex, it was alright" "Do you like her?" "Meh." Conversations with girls about sex can go on forever. Seriously. We can talk for hours about a 10 minute hook up.