Here are the most recent key figures about the 3 leading social networks Facebook, Twitter and YouTube. I liked the retro analysis which gives a good perspectives on their strenghts. Thought you might be interested. Make sure you open the 3 tables.
Facebook – source Mashable
source : Mashable et facebakers.com
Twitter – source : The Blog Herald
source : The Blog Herald
Youtube – source Flowtown
source : Flotown