A new article shows that Facebook was vulnerable to exploitation of it's "like" economy. Fake "likes" have been generated by bogus accounts possibly to manipulate public opinion.
Working with a computer scientist at Facebook and one in Lahore, Pakistan, the team found more than 50 sites offering free, fake "likes" for users' posts in exchange for access to their accounts, which were used to falsely "like" other sites in turn.
What this goes to show is that Facebook being a traditional system is insecure from attack. We cannot know whether likes are real or fake. Theoretically you can know for sure likes are real or fake on a Steem based platform because a Sybil attack has an economic cost. So at least in theory Steem offers an advantage in that.