Stack Exchange is doing an event this year in which... well, let me just use Aarthi's words:
Winter Bash 2012
Last year, on our Gaming site, we hosted an event called Hat Dash, where users earned "hats" for their gravatars by completing certain tasks (analogous to badges). Certain actions would trigger the user receiving a hat, which their gravatar could then "wear".
For example, editing a post would yield an editor-themed hat (fedora with pen) to the editor. [...]
This year, we're expanding the promotion to all sites which choose to participate, and redesigning the hat selection to be more appropriate to the entire network (no severed Wampa heads). Some of it is holiday-themed, some of it is a bit silly, and all of it is (hopefully) fun!
Some Nitty-Gritty
This event will run from 19 December 2012 to 4 January 2013. Users will be able to see their entire hat collection on http://winterba.sh. That site will also have a landing page, explaining the rules and other details of the event.
Individual users who don’t want to participate, don’t want to see hats, and/or are generally anti-hat will have an "I hate hats" option available, just as we had on Gaming last year.
The only visual change to the site itself will be the presence of the hats and the "I hate hats" button in the footer.
Here's a screenshot from last year's Hat Dash on Gaming SE:

As the message says, this can be disabled for each individual site and for each individual user. So if this is something you individually would not be interested in, you can just opt out, but if it's something the whole community would be uninterested in, we can just decide as a site not to participate. What do people think?