Although many mistake this abbreviation as 'What the fuck?' or 'World Taekwondo Federation', it actually stands for 'Welcome to Facebook!'. First coined by Abraham Lincoln in the late Jurassic Era, WTF became a popular phrase used by young people everywhere. Abraham Lincoln was shortly after assassinated by Communism, starting both the Vietnam War, and WWII (and the Cold War, if you really want to call it a war).
"WTF Mom!?! You added me on Facebook!?!"
"What does WTF mean young man!!"
"uhhh... Welcome to Facebook?"
"Ohh, thank you!"