Random Things I Don't Understand

Its 3 in the morning and yet my eyes were wide opening in front of my laptop browsing facebook while doing homeworks. There came this random little girl added me on facebook. Just by her name, I had no idea who she was. I went through her photos, more riddles popping out from my head. WHO THE EFF IS THIS?

I went on to see if I can get a clue by looking at our 5 mutual friends. 3 of them were my primary schoolmates and 2 are my cousins. Okay, so I thought, maybe I knew her. So I accepted her friend request and started a conversation with her.

MZ : Hey
Girl : Hi
Nice to meet you
MZ : Do I know you?
Girl : DUNNO
MZ : How you got my facebook account then?
Girl : c frm sum frenz lo
MZ : Ooh
Nice to meet you too anyway
Its kinda late
I have to go
Ciao

It was not until I said ciao that I deleted her from my facebook account. AWKWARD!

Now here's things I don't understand:
1. Why the eff are you adding people that you don't know?
2. Why the eff are you having 1051 friends even when you barely know 200 of them?
3. Why the eff my friends and cousins are your friends? Do you DUNNO them too?
4. Why am I asking why?

Perhaps I'm just jealous annoyed by people who are trying to expand their social networking by simply clicking the "Add As Friend" button on every profile they could find.

(P/S: answer for Q3: because my friends and cousins are whoring their profile too with 1200+ friends!!!)