2Dec/110
Study: Facebook friends are your age and from where you live
There are currently 721 million active Facebook users (more than 10% of the global population), with 69 billion friendships among them. The Laboratory for Web Algorithmics of the Università degli Studi di Milano just published a study of how these friends' age distribute. In short: Facebook users tend to have friends of about the same age, a pattern that holds true even for users aged 60.
Chart from Marketingscharts.com:
Data from the study indicates that Facebook friends are also very locally clustered, with 84% of all connections being between users in the same country.
Also from the research: the median friend count on Facebook is 100, while the average friend count is 190 - which is awfully close to Dunbar's number.