Big Data is data that exceeds the processing capacity of conventional database systems (http://radar.oreilly.com/2012/01/what-is-big-data.html). Billions of people and the popularity of internet accessible devices contribute to the large amount of data available today.
Recommended Reading on Big Data
Anderson, Janna and Lee Rainie, “The Future of Big Data”, July 20, 2012 (http://pewinternet.org/Reports/2012/Future-of-Big-Data/Overview.aspx)
Avanade, “Global Survey: The Business Impact of Big Data”, November 2010 (www.avanade.com/Documents/Research%20and%20Insights/Big%20Data%20Executive%20Summary%20FINAL%20SEOv.pdf)
Hswe, Patricia and Ann Holt, “Transforming Research Libraries: E-Science Guide to Research Libraries: The NSF Data Sharing Policy”, Association of Research Libraries (www.arl.org/rtl/eresearch/escien/nsf/index.shtml)