Stats

FIrstly, some Trend data on internet usage in general:

http://pewinternet.org/Trend-Data.aspx

Secondly, a super nice litlle study summing up age group differences online:
http://www.pewinternet.org/~/media//Files/Reports/2009/PIP_Generations_2009.pdf

This PEW is an American research institute of some kind, personally I got in touch with it via Stefana Broadbent's tedtalk How the Internet enables intimacy