As both individuals and businesses are starting to embrace social media, understanding the power and influence of social media becomes an important question. This dissertation aims to address this issue and study the impact of social media in different contexts. It consists of two essays. The first essay examines the effectiveness of social media as a marketing channel and quantifies the impact of artists' broadcasting activities on music sales. The second essay investigates the role of social media in financial markets and studies how peer-based advice expressed in social media affects stock prices. Both essays are empirical research based on data sets collected primarily from social media sites. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]