We always knew Facebook was big, but until the social network filed papers to become a publicly traded company, we didn't know exactly how big. Facebook is very close to hitting the one billion user mark, and as predicted, that will probably happen in 2012. The company also turned a tidy profit to the tune of $1 billion in 2011. More than half of Facebook's monthly active users visit the social network from mobile devices, and about 80 percent of Facebook's fans are outside the U.S. and Canada. [...]