I wonder if enough of the core-base was eroding that they were forced to make this change. I've been logged out of Facebook since October, and I know a few other friends who have as well. That's not really relevant, except that this group all had membership on Facebook at the 1 year mark - early 2005.
Facebook has become a kind of shit version of Reddit where everything in the news feed is basically stuff from Reddit that has been shared by friends. It used to be original messages from friends.