The personal page of Facebook founder Mark Zuckerberg was hacked and an unauthorised update was placed on it.
The update read: "Let the hacking begin: If Facebook needs money, instead of going to the banks, why doesn't Facebook let its users invest in Facebook in a social way? Why not transform Facebook into a 'social business' the way Nobel Prize winner Muhammad Yunus described it? What do you think? #hackercup2011"
French president Nicolas Sarkozy also had his Facebook account hacked recently. Hackers made it look like he had resigned.
Security is a major concern for users of social networking websites and the incident is embarrassing for Facebook.
Read commentary from Sophos' Graham Cluley on the subject here.