Their official stance is that these cookies are used for fraud detection: https://www.facebook.com/notes/alex-stamos/preserving-security-in-belgium/101536789442

Their official stance is that these cookies are used for fraud detection: https://www.facebook.com/notes/alex-stamos/preserving-security-in-belgium/10153678944202929 https://www.facebook.com/notes/alex-stamos/preserving-securi... In theory, Facebook could also sell these ghost profiles to web sites that have the Facebook like button or Facebook comments and want to show personalized ads.