It is said that Facebook is the “internet within the internet” and millions of businesses use it…with varying degrees of marketing success. Since Facebook has the participation of 96% of people 18-35 and is now the 3rd largest country in the world after China and India, it cannot really be ignored.
YouTube is another online phenom. Something like 46 years-worth of videos, accounting for over 70% of the activity on the internet, are watched every day at YouTube. This is the second most active search engine in the world after Google.
source : http://www.bluepoppy.com