The team at Flowtown.com designed the 2010 Social Networking Map as an update to the Map of Online Communities by xkcd.com in early 2007. Social networking has certainly advanced in the last three years (even in the last three days!), so the update shows a lot of changes in geography.
It does seem a little premature to claim this is the map of social media for 2010 with five months left to go. A lot can happen in five months (like the Apple PING service announced this week).