Trendstream’s Global Web Index has a visualization, Global Map of Social Web, that shows the uptake of different social media systems in 16 countries around the world.
Full size pdf
It’s a little busy, but it overlays a lot of information over the world map.
“The map visualises the number of active bloggers, social networkers, video sharers, photo uploaders and microbloggers. The length of the curve represents the penetration and the size represents the universe size. We have also included the actual numbers so you can use and apply the universe estimates.”
I was surprised to see the variation in popularity of the different modalities.