Which is already happened on facebook,i think they already blocks everything like advertising an ICO or anything related to it.If other would also ban cryptocurrency then IMO it would severely affect them.Social media is one of the good vessel for promoting and spreading facts about crypto currencies as it is the major platform that used by millions of people nationwide.However i don't think this will happen,maybe in some social media but not all of them and besides there are still other sites where crypto currencies are being tackled e.g. this forum.