Some recent emarketer data:

http://www.emarketer.com/Article.aspx?R=1007982

Email – is still the strongest channel for communication between peers however the trend is moving more towards social media for peer to peer communication.

The majority of 18-24 and 25- 34 year olds prefer social media over email.

Ways US Internet Users Share Content, by Age, Aug 2010 (% of respondents)

While the trend is moving strongly to social media for peer to peer content sharing the motivation is more self driven. The majority of users share what they find interesting or amusing NOT what they think others will find useful.

Primary Reason US Internet Users Share Content Online, Aug 2010 (% of respondents)

By Allan Levy| October 13th, 2010