Social media are media for social interaction, using highly accessible and scalable publishing techniques. Social media uses web-based technologies to turn communication into interactive dialogues. Andreas Kaplan and Michael Haenlein define social media as "a group of Internet-based applications that build on the ideological and technological foundations of Web 2.0, which allows the creation and exchange of user-generated content."¹

Understanding the impact and magnitude of social media is a daunting task perhaps because of its ever-changing landscape.

The approach taken by Box Hill Institute TAFE is an excellent snapshotof social media statistics for Australia that is both entertaining and informative.  

Reference 

1. Kaplan, Andreas M.; Michael Haenlein (2010). "Users of the world, unite! The challenges and opportunities of Social Media". Business Horizons 53 (1): 59–68. doi:10.1016/j.bushor.2009.09.003. ISSN 0007-6813. http://www.sciencedirect.com/science/article/B6W45-4XFF2S0-1/2/600db1bd6e0c9903c744aaf34b0b12e1. Retrieved 2010-09-15.