1) Something ripped out of them anime faces, literally used every post when it comes to those Wapanese, exaggerated anime fans, or generally any audience that tries to act like they were born from Japan.
2) A lot of asians don't even KNOW of this smiley.
3) If not used by the Wapanese, it is used to express some joy and generosity. Although ':)' is much better.
1) Fukai Fukai Moriiii, I love Inuyasha, kupo ^_^ I can translate it in english, kupo. ^_^