C. Li. Mcgraw-Hill Professional, (2008)Charlene Li works for Forrester Research, a company well-known for its research on social media. "Web-Strategist" Jeremiah Owyang whose blog is among the top50 ad-blogs world-wide (http://www.web-strategist.com/blog) also works there as an analyst. I heartily recommend his blog if you're interested in social media and its impact on the business world..
A. Back, N. Grau, and K. Tochtermann. Oldenburg Wissenschaftsverlag, Munich, (2008)Collection of articles of several authors / Case studies
Table of Contents : http://www.gbv.de/dms/zbw/556752635.pdf.