Procedings of the Joint 9th WEBKDD and 1st SNA-KDD Workshop 2007 Why We Twitter: Understanding Microblogging Usage and Communities Akshay Java, Xiaodan Song, Tim Finin, and Belle Tseng August 12, 2007 Microblogging is a new form of communication in which users can describe their current status in short posts distributed by instant messages, mobile phones, email or the Web. Twitter, a popular micro