It's not about knowing, it's about understanding.

You could tell the whole world "hey I'm a friend" but do you really think you worth claiming that title? 

Knowing lots of people doesn't makes you powerful neither awesome or whatever because when you need a pal just one friend to be there to listen to you pour out all your troubles and sorrows, when you need someone there to hang out with, when you need to do this one thing with just one friend, when you needs truthful opinions, when you are having this major crush and you need this one friend who will learn your secret and not tell anyone, when all that you're hoping for is just one friend who is there to understand.

 You would realize that there's no one there. 

-Ouch- That's when you felt pain and realize friend is a title, so vulnerable.