Facebook has created an empire...literally. I don't think I've ever seen a term so quickly become a household term like Facebook has. It's all I ever hear on campus now and I used it myself the other day to contact a group partner for one of my classes. They have a virtually unbreakable monopoly on the college market at this point.
However, I will say that a recent update to allow for a system of seeing literally almost every action one does did cause a bit of a stir. However, Mark responded and took care of the issue fairly quickly. I only hope Yahoo will be as competent because Facebook continues to grow if this does change hands.