Happened way back when I was still in high school and facebook was relatively new. We used to own a cyber cafe.

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The Guy: (Talking to other customers) I'll have you know that I'm a graduate in Computer Science! *Proceeds to boast about self and other bullshittery*

Others: *In awe*

Me: *Veeeery Skeptical*

A few days later...

The Guy: (Talks to me) Hey, there seems to be a problem with your internet. I can't log in on facebook.

Me: Could you try to do what you are doing again?

...

The Guy: See, doesn't work.

Me: Have you registered your account on facebook?

The Guy: Huh? What are you talking about? I have my Yahoo! mail.

Me: ..You need to register your email on facebook in order to log in.

The Guy: What?? I don't get it. I am registered and have a Yahoo! mail!

Me: *Brain Sigh*

(I proceed to help him register his email on facebook)

The Guy: Oh, you had to register on facebook! Now I get it! I thought that if you created an email you can immediately use that to log in to facebook.

Me: *Internal facepalm x1000*

(This guy is a Computer Science graduate? Oh PLEASE. )