The play of likes

If there is one person earning billions because you like some thing it is mark zukerberg. The foundation of Facebook is in its concept of likes. It is fascinating to note that one can only like something and not dislike. This gives confidence to users who publish their information in Facebook that no one will criticize or dislike their contribution. The only way to differentiate between something great and something not great in Facebook platform is the number of likes. A good contribution can gain you more likes than the other, but definitely not negative criticism. The confidence our friends in Facebook enjoy in sharing trivial things in Facebook is that you have an option to like or not like. There is no option to dislike. This creates another problem. What will one do it someone shares a picture of someone hurting somebody, or of someone losing something. Are you supposed to like that? Or remain quiet not expressing your opinion. Where is the option to strongly criticize this?