What does this all mean? Essentially, it means that every single thing you do on Facebook, and if you’re logged in, on other websites, is potentially tracked by Facebook, and saved on their servers.
However, with Facebook, there’s a twist. It has an entire engineering team dedicated to building tools to make data easier to query with SQL-like language built on top of Hadoop, with Hive, and, although Facebook claims that access is strictly controlled, some accounts say otherwise.
Really frightening in which detail facebook is aggregating data from it's users and how it seems to be handled internal.