Facebook has hit 100.5 million U.S. users Monday, December 7 2009 — up from 98.1 million a week ago, and has averaged a few million new domestic users over most of the last year, according to Inside Facebook. That makes the U.S. the first country to reach the 100 million threshold, although 70% of Facebook’s monthly active users live elsewhere. A week ago, the site announced it had surpassed 350 million members worldwide.
