The controversy which has drawn in British Prime Minister David Cameron illustrates the difficulty of setting a universal standard across the 1 billion-user social network.
Facebook banned beheading videos in May but recently lifted the prohibition. Cameron, whose right-leaning government has unveiled a range of initiatives to censor objectionable content online, said today that allowing the videos back on the site was "irresponsible."
Facebook said in a statement that it is working on ways to warn people about the content they might see.