Why does Amazon think my friend is a kidnapper?

About four years ago, an irate father in Minneapolis walked into his local Target shop with a complaint. He wanted to know why they were sending his daughter, who was still at school, vouchers for baby clothes and cots. Were they trying to encourage her to get pregnant?

When they telephoned to apologise a few days later he was more diffident. His daughter had fessed up: a child was due in a few months. But if dad hadn’t spotted any telltale signs of pregnancy, the shop had: she’d been rumbled by her recent purchases, in particular unscented lotions and certain dietary supplements. Some algorithm had spotted the significance of a sudden change in her buying habits, and triggered the ‘bombard with new‑baby offers’ subroutine.

But if you think that’s worrying…