Here's part 1:
Me: Did you see the comments on the pic I posted of you on facebook?
Unnamed Teen (UT): Yes.
Me: You should say "Thank you" to those who commented.
UT: No. I don't want anyone to know I'm on facebook.
Me: Ummm...you are fb friends with them and I tagged you in the photos so they already know.
UT: Yeah, but I don't comment. I just look at what you post.
Me: But people still know you are on there
UT: Yeah, but they forget.
Me: (Rolling my eyes) Oh, okay...THAT makes sense