Currently reading Surveillance Capitalism. It reminded me of this classic article by Charles Duhigg: . The answer: they figure out what people tend to buy at certain points in their lives, then compare that to what you're buying now. Then they send you coupons that don't look targeted. That is, if they think you're pregnant, they'll put coupons for wine next to the coupons for diapers and vitamins. If it's too obvious, people get spooked.

"The way people spend money is the most reliable and revealing window into their desires and beliefs.” -- Surveillance State, Inside China's Quest to Launch a New Era of Social Control