I also wouldn't base my main application on it, but as a developer I don't mind it for smaller apps.
Everybody has different uses for facebook, which is one of the reasons that it is so popular. To me, being able to see how ALL of your friends are doing is invaluable. I can log on and see the the state of my friends' lives, and not just my college friends, but people from any given stage of my life. I can find out where friend A is working, or whether friend B is single, etc.. It's ultimately about keeping connected.
Do you really want to be informed about friends who get married, but don't invite you to there wedding because your not in there inner circle, but exist in there pesudo friendship circle acqiured in college and maintained only through the convience of facebook. Or do you want to constantly read about friends who achieve certain success while you have not, or maybe the other way around, your successful and happy, and there not.
Such information I believe is better left to passing chance encounters as we all move on in our own lives after college or a particular job when we used facebook to stay connected.
your point on staying connected in given stages of peoples life is well taken, but other then close family and friends do you really want to know all that goes on in peoples lives when you should be busy living your own.