Digital Footprint

A digital footprint, also called data exhaust is a trail left by an entities' interactions in a digital environment; including their usage of TV, mobile phone, internet and world wide web, mobile web and other devices and sensors. Digital footprints provide data on what an entity has performed in the digital environment; and are valuable in assisting behavioral targeting, personalisation, targeted marketing, digital reputation, and other social media or social graphing services[1]. In social media, a digital footprint is the size of an individuals online presence; as it relates to the number of individuals they interact with. Source: [2].

Facebook's ability to quantify digital footprints leads to better click through rates and it's success as an advertising platform.