I know there's a fine line differentiating "social media" sites from everything else, but if a list like this is going to compare Flickr, Facebook and Blogger.com as if they're in a single category, then I don't see why sites like YouTube or Digg aren't included as well.
Odd that Myspace doesn't start until a few months in. What's up with that?
Also I'd love to see the U.S. (aka monetizable) chart.