Facebook unseated Google as the number one visited web site over the Christmas holiday, reports media blog Read Write Web.  Data from researcher Hitwise shows the social net was the top site in the U.S. on Christmas Eve and Christmas Day.  Facebook was number two behind Google during the holiday last year, and lagged behind Google and Yahoo Mail for most of 2009.   Read Write Web says that the Facebook-Google battle for web traffic is shaping up to be one to watch in the coming years.  Read more at Read Write Web {link no longer active}.