Without further notification Facebook changed the default behavior of how the messages of friends get presented to the user. By default, now only status updates of friends the user frequently interacts with are shown.
This often leads to a quite less crowded news feed. In this case, many users want the old behavior back. This change can be done easily. Just scroll down to the bottom of the news feed and find the “edit options” link on the right side next of “older entries”. Switch “show posts from” to “all of your friends and pages” and you should see everything again, just as before!
As a side note: Of course, Avira is on facebook, too!