Facebook’s quest for world dominance continues to gather pace, with the latest stats from the World Map of Social Networks showing that the platform has now become the number one choice for Brazilian netizens, beating down Orkut into second place.

Vincenzo Cosenza’s World Map of Social Networks, which gathers data from Alexa and Google Trends to compile its results, shows that Facebook now boasts more than 845 million active users (out of approximately 2 billion internet users worldwide), establishing itself as the social networking platform of choice in 126 countries across the world.

Several regions continue to resist Facebook’s empirical plans however, most notably Russia and several other former Soviet Union states, where Russian language platforms V Kontakte and Odnoklassniki maintain their iron grip. The Chinese government’s restriction of Facebook has severely hampered its penetration in a market dominated by QZone, while Iranian government restrictions have seen the Persian language site Cloob retake top spot from the US site.

Other hold outs include Latvia, where Dragulem is still the top dog, and Vietnam, where Zing remains king of the web.

Interestingly, back at home it seems as if the popularity of Facebook may have reached its peak, as the growth rate of new users slows to its lowest level since comScore.com began tracking its data in 2008. Last April saw the number of unique visitors on Facebook rise to 158 million, a rise of just 5% on April 2011.

Admittedly, Mark Zuckerberg’s site pretty much has the homegrown market sewn up already, but its decelerating growth rate, down 24% compared to April 2011, and 89% compared to April 2010, will certainly be cause for concern and perhaps add even more impetus to its drive for global dominance.