2013–2019 Meta / Facebook — Onavo & the "Research" App

Facebook bought the VPN app Onavo in 2013 for a reported $200M and marketed it as a tool to "protect" users — while it quietly logged which apps people used, how long, and what sites they visited. That data tipped Facebook off to WhatsApp's rise (which it then bought) and Snapchat's decline before the public knew. After Apple removed it, the same code lived on in a "Facebook Research" app that paid teenagers up to $20/month for root access to their phones. Apple revoked Facebook's developer certificate; Facebook shut Onavo down in 2019.