To bust or out someone's petty crimes or shameful actions via facebook pictures or wall posts.
"Sasha totally busted Candice for borrowing without asking."
"Andrew posted some pics of a dinner date with Candice and she was wearing Sasha's sweater in one of them."
"Dood, he soooo facebusted her!"
When one member of a facebook relationship decides to alter their relationship status to reflect a discontinuation ("single") or troubled/sketchy state ("it's complicated" or "in an open relationship") of said relationship unbeknownst to the other party or parties of that relationship.
Candice wrote on Greg's wall "never facebreakup with me again b/c it made me break out. love you!" when he cancelled their relationship on his facebook last weekend. Now they're "engaged".