Recent advances in data collection and computational statistics coupled with increases in computer processing power, along with the plunging costs of storage are making technologies to effectively analyze large sets of heterogeneous data ubiquitous. Applying such technologies (often referred to as big data technologies) to an ever growing number and variety of internal and external data sources, businesses and institutions can discover hidden correlations between data items, and extract actionable insights needed for innovation and economic growth. While on one hand big data technologies yield great promises, on the other hand, they raise critical security, privacy, and ethical issues, which if left unaddressed may become significant barriers to the fulfillment of expected opportunities and long-term success of big data. In this paper, we discuss the benefits of big data to individuals and society at large, focusing on seven key use cases: Big data for business optimization and customer analytics, big data and science, big data and health care, big data and finance, big data and the emerging energy distribution systems, big/open data as enablers of openness and efficiency in government, and big data security. In addition to benefits and opportunities, we discuss the security, privacy, and ethical issues at stake.