Facebook on Monday said that the World Cup has kicked up more action at the leading social network than any other event in history. More than a billion comments, posts, and likes related to World Cup matches have been racked up since the tournament began on June 12, in a level of online conversation never seen before at Facebook, according to the California-based social network. Knock-out matches that took place during the weekend pushed the overall number of interactions at Facebook past a billion. Facebook generally sees a large amount of conversation around sporting events, but the World Cup has proven to be a unique moment, the social network said in a blog post.