When you get on the computer to do something productive, but instead you instantly go into auto-drive and log onto Facebook and completely forget the real reason you even got on the computer.
Man, I was going to write my 10 page english essay until I was hit by brick wall of facebook-amnesia!
When people from earlier in your life whom you hated decide to friend you on Facebook as if you're old friends.
"David must have Facebook amnesia. He friended me even though I hated that little fucker back in high school."
A condition of thoughtlessness which occurs when you open up Facebook and forget what you are doing. It is usually temporary, and the person will eventually awake as if out of a stupor. Those who suffer from it are unable to retrieve information and instead fall into a state of oblivion. The most common symptom is mental blankness where the victim descends into a deep state of incognizance.
Danny: Dude, can you see what time the open mic is at?
Rob: Sure man, lemme just check on Facebook.
15 minutes later....
Danny: Bro! What the hell have you been doing for all this time?!
Rob: Oh, I, uh...just looking at some pictures of this girl who's a friend of a person I found on the wall of an acquaintance from middle school.
Danny: Broooo! Shit, stop it, she's like 16. You've got Facebook Amnesia! Now go and check the event page.