Zuckerberg was the target of a Facebook exploit
Khalil, a whitehat hacker discovered a bug which allowed people to post on any Facebook users timeline irregardless of any privacy settings they had in place.
Despite reporting this bug 3 times through Facebook’s whitehat page, he was ignored and told that this “was not a bug” by Facebook’s “Emrakul”, who is a security employee.
He went one step further and posted on Mark Zuckerberg’s wall, then uploading a screenshot to his own wall. Within minutes a software engineer at Facebook ( Ola Okelola ) replied asking for details about the exploit. Then his account was disabled.
After Facebook had fixed the bug, they re-activated his account but denied him the $500 promised to people who report critical bugs to Facebook.