Facebook Effect
The feeling of déjà vu one often experiences upon meeting someone one has friended or Facebooked, but has never actually met in person.
Person A: "I feel like I've met you before."
Person B: "Yeah. I feel the same way."
Person A {struck by a strong realization}: "Oh! Do you have Facebook?"
Person B {struck with similar sense as Person A}: "Yes I do. That's where I know you from!"
Person A: "Dude! We totally just experienced the Facebook Effect!"
Person B: "Crazy!"