According to Hitwise (ironically via their Twitter feed), Facebook was the #1 visited site in US on Christmas Eve and Christmas Day. This is the first time Facebook has been the most visited page.
Facebook's growth and audience diversity are obvious - but this is a telling sign that Facebook has matured beyond college audiences (who seasonally are not on-campus during late December) and into ubiquity. Over Christmas, my Facebook feed - like all others - featured best wishes, vacation photos, food updates, football analysis, etc.
A thank you to Facebook's Alex Schultz who posted this on his Facebook feed (where I found the tip!):