Interesting Facts and Figures about the most commonly used Social Networks

Knowing that today's news is tomorrow's history I still recommend to have a look at the following two websites and their "historic" information from earlier 2012. 
They contain some nice visualizations and interesting facts, figures and statistics about the most frequently used Social Networks on the planet (disregarding the special case of China with its own massive Social Networks here). 

Significant Social Media Facts, Figures and Statistics + Infographics

Fascinating Social Media Marketing Facts and Statistics for 2012