In the U.S. 60% of Internet users have Facebook accounts.  In Japan, only 2% of Internet users have Facebook accounts and services like Mixi, Gree and Mobage-town are 10 times as big.  According to a recent New York Times article, one of the primary reasons Facebook has failed to catch on in Japan is its insistence that people use real names when signing up for accounts.  Japanese Internet users fiercely guard their privacy, and, according to the article, even popular bloggers prefer to use nicknames or pseudonyms when socializing on the web.  It is interesting that even as technology makes the world a little smaller every day, there are still some very fundamental differences in how people choose to use the tools we now have access to.  The full article is worth a read.