Let's take the bright orange banner at the top of the screen that appears only to new users.
This is not displayed to new users only. It's also used to give registered users alerts about new answers to their questions, comments on their answers, changes to questions they are following, etc.
Seems to be a general purpose alerting/messaging feature which was then brought over to drawing attention to "new" visitors about what SO is.
This is not displayed to new users only. It's also used to give registered users alerts about new answers to their questions, comments on their answers, changes to questions they are following, etc.
Seems to be a general purpose alerting/messaging feature which was then brought over to drawing attention to "new" visitors about what SO is.