Black-flakking is the the act of tricking others into opening a link to the much talked about music video "Friday" by Rebecca Black. This trick is very similar to rickrolling. To be Black-flakked is to be the victim and the act of Black-flakking is done by the predator/troll. The prank is considered to be funny because the song is horrible in many, many ways.
Troll: Hey, dude, you should really check out this video! It's super hilarious and has monkeys!
(secretly sends link to "Friday" because they are
Victim: WTF?! That was the worst music I've ever heard!
Troll: You just got black-flakked! U mad, bro?