The fact that it's such a popular element of Facebook's functionality goes a long way in showing how important it is, both for the people clicking the button, and those on the receiving end.
Changing human behavior is often considered to be one of the hardest things to do in business and in life. Yet, there is a very reliable way that human behavior changes over the long-term.
How do you change someone's mind if you think you are right and he or she is wrong? Psychology reveals the last thing to do is the tactic we usually resort to.