While making some searches about Facebook usage (by Country, gender and age group) I came across a nice tool on AllFacebook.com – providing a line diagram based on Facebook’s own data in the last month. No privacy issues here, as it’s completely unrelated to personal profiles.
Make your own inquiries…
[the original tool I linked here is not working anymore – instead, visit this site]
Below, some data I found about Italian FB users in the 65+ age group (N.B. checksum fails because it’s not mandatory to declare your gender when signing in)