Why do i feel ignored on Facebook?

I only have 40 friends on facebook. I would say a few of them I don't really know, but we share mutual friends, and I guess that kinda makes it okay in round about way. But my concern is whenever I comment on something, nobody says anything back, they don't hit the "like" on or nothing. Even when I've wished someone a happy birthday, I sent personal message to them because i didnt want to be rejected in front of the facebook world. And sure enough, the one person in my friend's list i wished a happy birthday didn't acknowlege me at all. I have shared some really good news articles from Yahoo news, just about every one of them very helpful. And no one ever says anything. I am alone on the page. I don't see where the friend is in the frienship part of facebook. I am feeling really apprehensive. On the other hand, some of the people can say anything, no matter how small, and every one jumps on board. these are not necessarily my friends, but frineds of a friend. I don't really see the real purpose for Facebook. It is so clickish. can someone explain the politics of it.