As another example, Google has been collecting data on millions of people for years. You can view your "ad preferences" in your account, where it will tell you whether Google thinks you are male or female, how old you are, and what your interests are. I've seen whole reddit threads where people posted their ad preferences and which parts were true or false. Not surprisingly, they suck! This is the tech company with the smartest people in the world and the most data on their customers, yet they get more things wrong than right.