Marcus Wohlson tells us that analyzing our emotions by algorithms is not very accurate: “Even in the most stripped-down scenario however—where you assume everyone is being honest and unironic—sentiment analysis still has a long way to go. For basic binary choices, the most advanced sentiment analysis techniques have been shown to be between 70 and 80 percent accurate, says Marti Hearst, a professor at the University of California”
Wohlson also writes that for Facebook this is no problem: “… to sell to you, Facebook doesn’t have to know you perfectly. It just has to make a better guess than the competition.”