Stackexhcange is expanding the Winter Bash hat craziness that happened last year to the entire network. During the time period 19 December 2012 to 4 January 2013 whenever you do certain actions you will be rewarded at hat that your gravatar can wear. Those that don't wish to participate can of course opt out.
It was stated that individual communities can voice whehter they want to participate or not. We have until 28 November 2012 to voice whether we want to participate or not. If we don't respond we will be considered to have opted out.