This interesting, if simplistic, illustration from Valleywag shows you what's hot where. But, uh - no social networks in China or most of Africa? Or at best "unidentified" (which is also what Antarctica and Greenland show up as)? And what about places where two networks vie for dominance - how is that indicated?
The data comes from Alexa rankings, and it's good to see that it included Cyworld, which is both the world's oldest social network and the dominant player in South Korea, where 50% of the adult population has visited it.
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