Due to overwhelming support in favour of participating in Winter Bash 2014, I have informed SE that we're in. (I've locked the two poll answers to preserve the vote totals as they stand now for future reference.)
As always, even if math.SE doesn't opt out,1 individual users can still use the "I hate hats" option to hide the inanity.
The event will run between 15 December 2014 and 4 January 2015. There will be new hats and extra features to keep things fresh. On 5 January, all the hats will go back into storage for another year.
So, I ask again: Would you like some hats?
(SE would like to be informed of our decision before 1 December 2014. This will stay open until one option comes out as a clear favourite, or until 1 December, whichever comes first.)
1Okay, there is a difference: this year all sites are considered to be participating unless they inform SE otherwise.