Vincenzo Cosenza has compiled a world map of social networks–highlighting which networks are the most popular in each country.
As you can see, head to Brazil and you’ll find Google’s Orkut thriving. Take a trip to Russia and you’ll see Facebook clone Vkontakte holding firm.
I was able to find a similar map from June 2007. It’s easy to see just how quickly Facebook is taking over the world:
PS. If you prefer tabled data, here’s the 2009 breakdown: