Some Facebook stats:
from Facebook on 9/17/09:
http://www.facebook.com/press/info.php?statistics
More than 300 million active users
50% of our active users log on to Facebook in any given day
The fastest growing demographic is those 35 years old and older
Average user has 130 friends on the site
More than 6 billion minutes are spent on Facebook each day (worldwide)
More than 40 million status updates each day
More than 10 million users become fans of Pages each day
More than 2 billion photos uploaded to the site each month
More than 14 million videos uploaded each month
More than 2 billion pieces of content (web links, news stories, blog posts, notes, photos, etc.) shared each week
More than 3 million events created each month
More than 45 million active user groups exist on the site
and they have advertisements and sponsors