Social Networks and Social Norms

Recently I had a birthday.  I turned 24.  It provoked a lot of thought. Not the "gee I'm old" kind of thought, but more thoughts about how much the world is changing.
When I was a child, a birthday was marked by a celebration with the people closest to the one having the birthday - family, classmates, etc.  Grandparents might call and wish happy birthday or maybe send a card.  Classmates you saw every day would say happy birthday.  In most cases, the wishes were personal, face-to-face, and in real time. Thank-you's (with the exception of gifts and cards send by relatives far away) were also done face-to-face and in real time.
My birthday this year was different, much like it has been the last few years, really, since the entrance of Facebook into my life. Facebook is a wonderful tool for keeping up with friends and acquaintances, but it also seems to be changing the way things are done.  One thing that makes facebook wonderful is that it reminds you of when your birthday is.  It also reminds you when any of your "friends" have birthdays.  In any given week I'll get reminders of birthday for half a dozen or more people.  Some of whom I don't even really know.  Many of whom I haven't communicated with since their birthday a year ago, but have creepily followed by watching their newsfeeds and photos and notes.
So here's what happens when it's your birthday on facebook:
Before it's even your birthday in the time zone you are currently living in, friends in other time zones will start posting birthday wishes on your wall.  This will continue over the next 24-30 hours.  Most of them will be pretty basic "Happy Birthday *insert name here*!" Some will have generic well wishes tacked on such as "Have a great day!" or "I pray your day is full of blessings!" Some people get more creative with posts such as "It's your birthday, and that makes me happy. If you weren't born, I wouldn't know you. And if I didn't know you, my life would be worse for the wear. And if my life were worse...well...I'm not quite sure what'd happen. But I'm glad that you were born. I'm even more glad that you're still alive. [G-d] has definitely had his hand on you over the past few years....shoot...ever since you've been born." (LR) or "i pray that your celebration of your womb emancipation is blessed!" (BP)
You might get 100 or more birthday wishes over the course of your birthday.  Now, you, as the birthday haver, have a responsibility. You have to thank everyone for the birthday wishes.  In the past, this was mostly done in real time, and typically there were less of them.  Now, you either make a blanket statement in your status thanking everyone for the birthday wishes or you comment on every wall post....the latter of course is more time consuming and often considered the more socially acceptable. 
Facebook, and other social networks, seem to be changing our social norms.  Things aren't considered "official" until they are facebook official, as evidenced by this wall post: "I wished you a happy birthday this morning, but wanted to make it Facebook official - Happy Birthday, Joy! Celebrating your blessings with you! :)"  (JE)
I'm not sure what it is, but something about putting something on facebook somehow makes it more official, whatever that means.
I'm not sure how I feel about the way social networking is changing our society.  We know more people, but we tend to know them at a shallower level.   I have almost 700 "friends" on facebook.  I can click over to any one of their homepages and see pictures of what they did last weekend or read what their other friends have written on their walls, all without them ever knowing.  Likewise, any of my "friends" can click over to my homepage.  
Social networking allows for us to have contact with our friends when we want it, when it is convenient for us. And, if someone makes us angry, we can simply "un-friend" them and erase them from our lives.
What does this mean for real life community?  How is facebook changing the way that we relate to other humans?  How will the changes we are seeing now affect our children?  our grandchildren?  I don't have answers to these questions.  I don't even know all the questions, but they are things that make me think.
What do you think?