No longer do you need to be in the dark [Forbes article seems to have been taken down - LOL]:
Target assigns every customer a Guest ID number, tied to their credit card, name, or email address that becomes a bucket that stores a history of everything they’ve bought and any demographic information Target has collected from them or bought from other sources. Using that, Pole looked at historical buying data for all the ladies who had signed up for Target baby registries in the past.
So Target started sending coupons for baby items to customers according to their pregnancy scores. Duhigg shares an anecdote — so good that it sounds made up — that conveys how eerily accurate the targeting is. An angry man went into a Target outside of Minneapolis, demanding to talk to a manager:
“My daughter got this in the mail!” he said. “She’s still in high school, and you’re sending her coupons for baby clothes and cribs? Are you trying to encourage her to get pregnant?”
Turns out Target was right – she’d joined the club. Parents – never throw that junk mail in the trash.