foursquare Labs, Inc., is a location-based social network in which its more than 10 million users check in via a smartphone app or SMS to exchange travel tips and to share their location with friends.
To perform analytics across more than 5 million daily check-ins, foursquare uses Amazon Elastic MapReduce, Amazon EC2 Spot Instances, Amazon S3, and open-source technologies Mongodb and Apache Flume.