Turns out that many of them were doing the same thing–the Facebook part, that is. Web traffic-watcher Hitwise says Mark Zuckerberg’s site accounted for 1.93 percent of all U.S. Internet visits on New Year’s Eve. That’s up 75 percent from a year ago, when 1.11 percent of you checked in at the site at some point in the day.

But New Year’s wasn’t Facebook’s busiest day last month. That distinction belongs to Christmas Eve, when it set a site record of 2.18 percent of U.S. Internet visits, up from 1.42 percent in 2007.

You can draw your own conclusions about what those stats mean, or read Hitwise analyst Heather Hopkins’s theories here–she thinks snowstorms in the Northeast kept people trapped in their homes with nothing to do but post on their pals’ walls.

But I think the best explanation here is the simplest one: Contrary to predictions that Facebook would burn out as its core college audience grew tired of it, the site has continued to grow–it now claims 140 million active users worldwide. So you’re going to see records like this broken a few times a year.