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.

Yup, more of the same: Holiday sales from Nov. 1 through Dec. 19 are down one percent compared to the same period in 2007. Which is right in line with comScore’s (SCOR) prediction of flat online sales for the holiday.

If you’d like a rosier glow to these numbers, comScore tries to oblige, by noting that average online spending between Thanksgiving and Dec. 19 is actually up five percent per day. But since there are fewer days between Thanksgiving and Christmas this year compared to previous years, that won’t help retailers’ top or bottom lines.

What are people buying on Amazon (AMZN) and other electronic storefronts? Fewer flat screen TVs, ComScore says, either because promotional discounts have tapered off or because those who need a 42-inch LCD on their walls have already got one.

Meanwhile, I’m not sure what constitutes an online “Sports and Fitness” purchase, but ComScore says people have been making many more of them this year, because the category is up 31 percent. Music, movies and videos are much more familiar, and much less popular. Sales are down 24 percent, which mirrors what Best Buy (BBY) said about its brick and mortar sales for the same goods earlier this month.