In February 2008, in my What is Web 2.0 blog post I showed the following map about Social Networks, which came from xkcd.
Today, I saw on Le Journal du Geek the 2010 version and it speaks by itself. Notice the rise of FaceBook, YouTube, and Google for example but also the decline of MySpace and some others.
Only two years and an half between the two pictures. Changes are fast on the internet.