This document discusses big data use cases that use Amazon Elastic MapReduce (EMR) and Hadoop. It provides examples of companies like a big box retailer, Etsy, Yelp, and Foursquare using EMR to perform clickstream analysis, recommendations, process large amounts of log data, and analyze user check-in patterns at massive scales impossible without these cloud big data tools. EMR allows these companies to easily experiment and process massive datasets across large clusters of servers in an on-demand, flexible, and cost-effective manner in the cloud.