Facebook letdown
When you meet a girl or guy in person then proceed to add them on facebook and realize they are not as attractive as initially perceived upon first impression. Often, this first meeting will take place while intoxicated or in a dark place, such as a bar. Initial feelings of excitement and anticipation build as you have met a potential new love interest, only to be "letdown" while scouring countless facebook pictures of your so-thought object of desire.
"Dude, did you see that smoking hot chick I met at Tin Roof last night? I've been texting her all day" - "Hold on. She just accepted my friend request...wait..is that her? No way that's her. Aww man, yep, that's her, wow...dang it! What a Facebook letdown."