I may have a facebook account, but if people think I am going to check everyone's page every single day just in case they are announcing something "important", they are sadly mistaken.
It's just like the thread about "It was on my blog!"
Posting something on the internet, whether on a personal blog, facebook, myspace, or what ever other places there are, is not a way of notifying all one's friends and family of something.
I think, if one wants their friends / family / colleagues / etc to know something, it would really not be too much to ask to send an email or make a phonecall.
Edited to add: oh, and also! If something happens in my life that I only want certain people to know (my facebook friend circle is rather elaborate), I am most certainly not going to post it on facebook and start messing with all kinds of privacy settings to let just these people know and hide it from others. I will mail or phone to who it concerns. Facebook, to me, is more something for fun and leisure. More like a toy - definitely not a medium for official announcements or something that I allow to become a requirement.