It took Radio 38 years to reach 50 million listeners in the USA.
It took Terrestrial TV 13 years to reach 50 million viewers in the USA.
It took Facebook.com 9 months to reach 100 million users areound the world.
As of January 2010 Linkedin.com had 55 million registered users.
Traffic on twitter.com increased by 43% on the day of the US elections in 2008.
There is an estimated 900,000 new blogs created on a daily basis around the world.
As of January 2010 Wikepedia.com had 60 million visitors / month.