"Big Brother is watching you" is a quote from George Orwell's book "1984". It comments on how the government monitors and controls its citizens by suppressing the will of the populace. The phrase is often used to describe the dangers of mass surveillance and the loss of privacy in modern society. 

Social media platforms track user behavior and collect data on their preferences, interests, and habits. This data is then used to create personalized content and advertisements that are tailored to each user. While this can be convenient and entertaining, it can also be used to manipulate users and influence their behavior. It is important to be aware of these risks and to take steps to protect your privacy online.