Selfie? Hmmmmmm...well I frequently hijack my friend's phone, make hideous faces, crop them down until it's just a little square of horror, and then turn on the noir filter so I look like a demon. Does that count?
the first was because i realised i dont haev any pics of myself.
the second was because i was walking home from my grandmothers house and suddenly a chicken appeared in front of me on the street. it was so random i wanted to take a pic of us.
If you asked me 2 or more years ago, I would have said Armor Games. If your argument is that Armor Games never was a social network, girrl please. Look at that comment count and tell me you've talked to half that many people on Facebook.
Personally I like Facebook the best. I like being able to chat with my friends there and having events and stuff all in one place. Twitter is nicer for talking to people you aren't irl friends with though and those you don't want on your FB.
I don't use any of them, but my favorite from what I've seen and heard would be LinkedIn because it serves a more practical purpose than just chatting with people.